The Top 15 Things to Do in Houston: Must-Visit Spots for 2026

    15 things to do in Houston, from Space Center Houston and the Museum District to Buffalo Bayou Park, the downtown tunnels, and free art at the Menil.

    Last updated October 28, 2026

    Houston offers things to do that range from underground tunnel systems spanning over six miles and 95 city blocks to museums and a zoo housing more than 4,000 animals. The city doesn't rely on a single draw.

    Specificity separates the best things to do in Houston from the rest. The strongest ones deliver something concrete: artifacts you can see and green space you can walk. Animals you can watch. We've focused on attractions in Houston that stay relevant year-round and give you something tangible.

    Space Center Houston

    Overview

    Space Center Houston operates as the official visitor center for NASA Johnson Space Center. It gives you access to the heart of America's human spaceflight program. The facility spans 250,000 square feet and houses more than 400 space artifacts. This isn't a themed entertainment center. You're looking at actual command modules that orbited the Moon. You can touch rocks brought back from lunar missions and walk through training facilities where astronauts prepare for current space station rotations.

    The center opened in 1992 and functions as a nonprofit educational foundation rather than a government facility. That structure allows it to partner directly with NASA Johnson Space Center next door, the training base for NASA astronauts and home of Mission Control. Visitors get access to working government facilities through guided tram tours that leave from the main complex because of this partnership.

    Highlights

    The NASA Tram Tours form the core experience. Three tours operate at no additional charge with general admission: the Astronaut Training Facility tour takes you through active training areas, the NASA Campus tour covers multiple Johnson Space Center buildings, and the Rocket Park tour brings you to one of three remaining Saturn V rockets. This particular Saturn V uses flight-ready components from canceled Apollo missions 18, 19 and 20. A fourth option, the Historic Mission Control tour, requires a separate ticket booked in advance and takes you into the actual control room used during Apollo missions.

    Starship Gallery holds flown spacecraft. These include the Apollo 17 Command Module from the final Moon landing, the Mercury 9 and Gemini 5 capsules, and the Skylab trainer where astronauts first learned to live in space for extended periods. You can walk inside both a high-fidelity Space Shuttle replica and the original NASA 905 shuttle carrier aircraft that transported shuttles between locations at Independence Plaza. This combination exists nowhere else.

    The International Space Station Gallery displays actual flown artifacts from the station among interactive demonstrations. Mission Mars lets you touch a meteorite from the red planet and climb into an Orion capsule trainer. Actor Tom Hanks narrates "The Moonwalkers," a theater presentation covering lunar exploration history that comes with general admission.

    Visitor Information

    The center opens at 10 a.m. daily and closes at 5 p.m. on weekdays, often later on weekends. It closes on Thanksgiving and Christmas. Parking runs separately from admission, though members receive it at no charge. Tram tours last 60 to 90 minutes depending on which stops you choose. These run on open-air trams, so weather affects operations and you'll want to dress for the conditions.

    You can bring small bags, cameras (without tripods or lenses longer than six inches), and comfortable walking shoes. The facility prohibits luggage, large camera equipment, coolers with large food quantities, and pets except service animals. Food isn't allowed on tram tours, though you can bring water bottles with sealed lids. Strollers stay parked at the tram boarding area.

    Tours visit active NASA facilities that can close without notice for operational reasons. Historic Mission Control often sells out days ahead during weekends and school breaks, so booking two weeks in advance makes sense for that specific tour.

    Museum of Fine Arts Houston

    Overview

    The Museum of Fine Arts, Houston holds nearly 80,000 works spanning more than 5,000 years of history from six continents. Size matters here because it affects what you can see in a single visit. The collection spreads across three main buildings on the Sarofim Campus: the Caroline Wiess Law Building for pre-Columbian and Asian art, the Audrey Jones Beck Building for European and Egyptian pieces, and the Nancy and Rich Kinder Building for contemporary and modern works. Two additional house museums, Bayou Bend and Rienzi, operate at separate locations near Memorial Park.

    The museum opened in 1924 and became the oldest art museum in Texas. It ranks as the tenth-largest museum worldwide and the second-largest art museum in the Americas by gallery space. Over 900,000 people visited in 2023.

    Highlights

    Current exhibitions run through 2026 and into 2027. "Harry Bertoia: Echoes in Space" continues through April 11, 2027, and "From Persia to Paisley: Global Luxury and the Kashmir Shawl" runs into summer 2027. The ongoing Yayoi Kusama installation "Aftermath of Obliteration of Eternity" stays in the Kinder Building indefinitely.

    The permanent collection has dedicated galleries for Islamic art, Korean art, Judaica, and contemporary works. Spanish Viceregal paintings and works from the al-Sabah Collection rotate through regular display.

    Visitor Information

    The Sarofim Campus operates Sunday 12:30 p.m. to 6 p.m., Wednesday 11 a.m. to 5 p.m., Thursday and Friday 11 a.m. to 9 p.m., and Saturday 11 a.m. to 6 p.m.. The museum closes Monday and Tuesday. Thursday admission to permanent collections is free for all visitors. Children 12 and younger enter at no charge any day.

    Parking garages charge a reduced rate for members on stays between 31 minutes and four hours, with a higher rate for non-members. METRO rail stops adjacent to the museum.

    Buffalo Bayou Park

    Overview

    Buffalo Bayou Park stretches 2.3 miles along the waterway west of downtown, covering 160 acres between Shepherd Drive and Sabine Street. The park opened in October 2015 through collaboration with Buffalo Bayou Partnership, the Kinder Foundation, Houston Parks & Recreation Department, and Harris County Flood Control District. What makes this green space work as one of the best things to do in Houston comes down to how it balances active recreation with natural landscape. You'll find hike and bike trails running the full length, native gardens, a nature play area, and spots where the bayou itself becomes available.

    The 26-mile paddling trail represents the first of its kind in Houston and requires no prior experience. On land, a wide concrete trail along both banks is shared by walkers, runners and cyclists, while a narrower asphalt footpath between Shepherd and Sabine is reserved for pedestrians.

    Sunset Bat Bridge Guided Kayak Tour in Houston
    Credit: Buffalo Bayou Kayak Tours

    Highlights

    Johnny Steele Dog Park spans 2 acres with separate zones for large and small dogs, plus a swimming pond and washing stations. The park opens daily from 7 a.m. to 8 p.m. It closes Tuesdays from 7 a.m. to 4 p.m. to maintain the grounds and Fridays from 1 to 2:30 p.m. to clean the pond.

    The 30,000-square-foot skate park completed construction in 2008, with a renovation following in 2016 and 2017. Barbara Fish Daniel Nature Play Area has a boulder scramble, waterfall, sandpit, climbing logs, and a treehouse with climbing net.

    The Cistern operates as an 87,500-square-foot space for visual art and sound installations. This former water reservoir was decommissioned in 2007 and opened to the public in May 2016 with its first exhibition debuting that December. Hours run Wednesday through Sunday, 10 a.m. to 6 p.m..

    Visitor Information

    Lighted areas stay open from 6 a.m. to 11 p.m., while other sections operate dawn to dusk. The Water Works visitor center and Bayou Boutique operate daily from 9 a.m. to 6 p.m. and offer snacks and drinks. FLORA, A Mexican Kitchen sits at Lost Lake. Food trucks rotate through The Water Works entry court during the week.

    Parking operates at three main locations: The Water Works on Sabine Street, City Lot H at 1643 Memorial Drive with over 400 spaces, and along Allen Parkway between Sabine and Taft streets with 140 spots available 9 a.m. to 7 p.m. daily.

    The Houston Zoo

    Overview

    The Houston Zoo houses about 4,300 animals representing more than 600 species across its grounds in Hermann Park. This collection makes it one of the most visited attractions in Houston and pulls people who want to see everything from African elephants to Texas wildlife in naturalistic habitats. The facility operates as a nonprofit conservation organization that funds field projects in Texas and around the world. Your visit connects to broader wildlife protection efforts.

    What separates the zoo experience here from typical tourist things to do in Houston relates to scale and breadth. You're not walking through a small urban facility. The grounds cover enough territory that you'll want comfortable shoes and a plan for which exhibits matter most to your group.

    Highlights

    Animal encounters run throughout the day and give you closer access to residents with keeper guidance. These scheduled programs vary by season and include reptile house tours, elephant interactions, and golf cart tours through select habitats after regular hours. The encounters require separate arrangements beyond general admission.

    Meet the Keeper Chats happen at scheduled times and let you hear from staff about animal care and conservation work. The Wildlife Carousel provides a break for younger visitors, while the Children's Zoo section focuses on farm animals and hands-on experiences.

    Special events populate the calendar year-round, from weekend celebrations to conservation-focused programming. Members receive early notifications about these events, so they get first access to limited-capacity programs.

    Visitor Information

    The zoo operates 9 a.m. to 5 p.m. daily, with last entry at 4 p.m. It stays open seven days a week, closing on Christmas Eve and during the day on Thanksgiving and Christmas, when it reopens in the evening for Zoo Lights. Non-member guests must make online reservations through timed tickets, while members can enter without advance booking. Tickets aren't sold at the gate, so planning ahead matters if you're visiting without a membership.

    Hermann Park

    Overview

    A 445-acre green space sits minutes from downtown Houston and functions as both recreational ground and cultural anchor. Hermann Park borders the Texas Medical Center, Rice University, and the Museum District. This puts it within reach of multiple neighborhoods. The park's design reflects its role as a multi-purpose space where people come to play golf, attend outdoor theater performances, or walk Japanese Gardens during the same visit.

    Explore Hermann Park Ghost Tour in Houston
    Credit: Houston Ghost Tour

    The Heart of the Park project altered 18.5 acres between 2004 completion and present day. That renovation earned a General Design Award of Excellence from the American Society of Landscape Architects in July 2005. The award recognized the physical improvements made to this central zone.

    Highlights

    The Mary Gibbs and Jesse H. Jones Reflection Pool stretches 740 feet long and 80 feet wide. Eighty-year-old live oak trees border it. Its black bottom was designed to boost water reflectivity. The Sam Houston Monument and Circle frame the north end of this area, while Lake Overlook fronts McGovern Lake to the south.

    McGovern Lake hosts pedal boat activity through the Pedal Boat Lagoon starting point. Each boat accommodates up to four people and brings you close to ducks, waterfowl, and fish visible below the surface. The experience takes you onto the water rather than just viewing it from shore.

    Miller Outdoor Theater and Hermann Park Golf Course operate within the grounds. Japanese Gardens and Rose Garden provide planted landscapes distinct from the native oak groves.

    Visitor Information

    Shaded walking paths use decomposed granite surfaces. Benches group along routes between the reflection pool and lake areas. The live oak canopy provides cover during warmer months, therefore making morning and late afternoon walks more comfortable than midday visits.

    Houston Museum of Natural Science

    Overview

    The Houston Museum and Scientific Society founded the Houston Museum of Natural Science in 1909. It sits on the northern border of Hermann Park. The facility spans four floors of permanent halls, the Burke Baker Planetarium, the Cockrell Butterfly Center and the Wortham Giant Screen Theater. The museum received 1,547,000 visitors in 2024. This made it the eleventh most-visited museum in the United States and the third most-visited science museum in the country.

    This differs from typical fun things to do in Houston because of its dual nature. You walk through traditional museum displays and interactive experiences that make scientific concepts available without simplifying them.

    Highlights

    The Morian Hall of Paleontology operates as the largest paleontology hall in the United States. It contains over 60 major skeleton mounts. These include three Tyrannosaurus specimens, a Diplodocus and the most complete Triceratops skeleton ever found. The Cullen Hall of Gems & Minerals is closed for a multi-year renovation, though a selection of its specimens is on view in the first-floor Hamill Gallery. The Wiess Energy Hall spans 30,000 square feet with 16 sections. You'll find a working replica of an offshore drilling rig drill floor and the Geovator, a simulated trip into the rock beneath Houston.

    Welch Hall: Matter & Motion opened in 2024. It teaches chemistry and physics through interactive screens and displays. The Hall of Ancient Egypt houses millennia-old artifacts with recreations of Egyptian temples. The Cockrell Butterfly Center occupies a three-story glass building filled with tropical plants and live butterflies from multiple species.

    Visitor Information

    Hours run 9 a.m. to 5 p.m. Monday through Thursday and 9 a.m. to 6 p.m. Friday through Sunday, with Tuesday hours stretching to 8 p.m. Permanent exhibit halls offer free admission Tuesdays from 5 p.m. to 8 p.m., with last entry at 7:30 p.m.. The parking garage charges non-members a flat rate. Free three-hour parking operates at McGovern Centennial Gardens and near the Houston Zoo in Hermann Park lots.

    The Menil Collection

    Overview

    The Menil Collection charges no admission, and that policy extends to every visit, every day the museum operates. John and Dominique de Menil founded the facility, which opened to the public on June 7, 1987. They believed that art is essential to the human experience. The campus occupies 30 acres in a residential neighborhood and spreads across multiple buildings rather than concentrating everything under one roof. The main building sits at 1533 Sul Ross Street. You'll find the Menil Drawing Institute at 1412 W Main Street, the Cy Twombly Gallery at 1501 Branard Street, and the Dan Flavin Installation at Richmond Hall at 1500 Richmond Avenue.

    The permanent collection holds more than 25,000 objects that span prehistoric artifacts to contemporary pieces. Only about 5% displays at any given time, therefore keeping repeat visits fresh through rotation. Dominique de Menil wanted this approach because she believed continual rotation would maintain public interest.

    Highlights

    The collection holds over 1,000 examples of Max Ernst's work and several of René Magritte's most regarded paintings. Pieces by Yves Tanguy, Marcel Duchamp, Henri Matisse, Jackson Pollock, Pablo Picasso, Andy Warhol, Mark Rothko, and Cy Twombly fill the galleries. The museum also houses substantial holdings that include more than 900 African works from West and Central regions, over 800 pieces from indigenous Americas, and antiquities from classical and Byzantine periods.

    Current exhibitions through 2026 include "Wall Drawing Series: Jitish Kallat" at the Menil Drawing Institute running until August 8, 2027, and "Fragility" continuing through January 24, 2027. "Terry Winters: Vitalized Geometry" runs through April 4, 2027.

    Visitor Information

    The museum operates Wednesday through Sunday, 11 a.m. to 7 p.m. It closes Mondays and Tuesdays. Natural lighting fills the galleries, which were designed for intimate viewing experiences. Photography isn't permitted inside galleries, though you can shoot in entryways and hallways. Groups larger than 15 people need reservations. Groups of 30 or more require at least one week's notice. Parking sits at 1515 West Alabama Street and next to Richmond Hall.

    Discovery Green

    Overview

    Year-round programming defines Discovery Green's identity as an activity hub rather than passive green space. This 12-acre park operates between the George R. Brown Convention Center and the Marriott Marquis and Hilton Americas-Houston hotels in the downtown core. The layout has open lawns, shaded walking areas, a one-acre lake, the John P. McGovern Playground, and Gateway Fountain. What makes this one of the best things to do in Houston relates to its nonprofit management structure through Discovery Green Conservancy, so programming flexibility exists that municipal parks lack.

    Highlights

    Seasonal attractions change throughout the year. An ice rink operates during winter months and a roller rink appears in spring. The calendar fills with concerts, cultural festivals, outdoor movie screenings, and fitness programming that has yoga, tai chi, and hip hop yoga sessions. Bumper boats and cruiser boats operate on Kinder Lake and provide motorized water access. Public art rotates through the space. Recent installations had eight 20-foot sculptures that depicted creatures from Mexican magical realism. The Grove and Lake House provide on-site dining.

    Visitor Information

    The park opens from 6 a.m. to 11 p.m. daily, with extended hours until midnight during summer. Restrooms operate 9 a.m. to 11 p.m., while family changing rooms near the fountains stay open 9 a.m. to 9 p.m.. Gateway Fountain runs 9 a.m. to 7 p.m. daily and extends to 9 p.m. in summer. The park information center at Alkek Building answers questions seven days weekly from 9 a.m. to 6 p.m.. Admission requires no payment.

    Houston Livestock Show and Rodeo

    Overview

    The world's largest livestock exhibition and rodeo runs each year in Houston and draws millions of visitors to a 20-day event that combines professional rodeo competition, livestock shows and concerts. This celebration of Western heritage and agriculture has grown from a small regional exhibition into one of the largest cultural events in the United States since 1932. Attendance reached a record 2.74 million in 2025, and the 2026 event drew about 2.62 million. The event operates through a nonprofit structure focused on promoting agriculture, educating the public and supporting Texas youth through scholarships.

    Highlights

    RODEOHOUSTON functions as a tournament-style competition in eight rodeo events: bareback riding, bull riding, saddle bronc riding, steer wrestling, tie-down roping, team roping, women's barrel racing and breakaway roping. The purse runs into the millions, and each event champion takes home a cash prize plus previous round winnings, a custom saddle and belt buckle. The competition advances through five three-day Super Series, Semifinal rounds, Wild Card rounds and a Championship Shootout.

    The World's Championship Bar-B-Que Contest brings over 250 teams competing across multiple categories beyond rodeo action. Traditional trail rides meet at Memorial Park before the opening parade.

    Visitor Information

    The 2027 event runs March 2-21 at Reliant Stadium and Reliant Park. Special days include Armed Forces Day, Black Heritage Day, First Responders Day and Go Tejano Day throughout the schedule.

    Contemporary Arts Museum Houston

    Overview

    Contemporary art in Houston becomes available without barriers at Contemporary Arts Museum Houston, where admission remains free every day the doors open. This policy removes the financial decision from your visit. You can drop in for an hour or return multiple times without calculating cost per visit. The museum focuses exclusively on contemporary works and distinguishes itself from encyclopedic institutions that span centuries.

    Highlights

    Current exhibitions rotate through the galleries and present works that involve present-day concerns and artistic practices. Recent programming has "Mary Ellen Carroll: How To Talk Dirty and Influence People" among "Divination: Beverly Buchanan & Dionne Lee," both on view at the present time. The museum's commitment to contemporary art means exhibitions change often, so return visits prove worthwhile for anyone tracking current artistic movements.

    Visitor Information

    Operating hours run Wednesday through Sunday. The museum closes at 6:00 p.m. on most days and extends to 9:00 p.m. on Thursdays. Plan for one hour to move through the exhibits at a comfortable pace. The extended Thursday hours work for anyone whose schedule doesn't line up with typical museum visiting times during weekday afternoons.

    The Galleria

    Overview

    Shopping drives The Galleria's identity, yet the complex delivers attractions in Houston beyond retail. This indoor destination combines stores with year-round ice skating. You can glide across ice beneath a glass atrium after browsing multiple levels of shops. The location serves the Uptown area at 5085 Westheimer Road and acts as both a shopping hub and an entertainment venue that stays active whatever Houston's weather.

    Highlights

    Ice at the Galleria operates as a year-round indoor rink positioned in the Center Food Court level. You'll skate beneath a glass dome while viewing the mall's multi-level surroundings. Public skating sessions run throughout the week. Learn to Skate classes start sessions in late August for eight-week periods. The rink also hosts broomball, group events and birthday parties beyond standard skating times.

    The Galleria and Uptown district offer dining that ranges from casual to upscale categories. Coffee shops and restaurants with Mexican coastal cuisine, steakhouse fare and Indian flavors populate the area.

    Visitor Information

    The Orange Parking Garage at 5050 West Alabama provides the most direct access to the ice rink. The Yellow Garage at the Westheimer and McCue intersection is another option, and standard garage parking at the Galleria is free.

    Houston Botanic Garden

    Overview

    A former city-owned golf course became a 132-acre botanical destination that opened in September 2020 following construction that began in spring 2019. Houston Botanic Garden involves all five senses rather than relying on visual appeal alone. You'll hear wildlife drawn to natural ecosystems and smell pine groves and distinct botanical fragrances. You can reach out to touch simple machines in water play areas. The facility showcases over 1,100 different plant taxa. These span formally designed gardens and rolling prairie-like landscape dotted with grand oaks and pines.

    Highlights

    The Global Collection Garden spans three acres with more than 400 plant species from tropical, subtropical, and arid climate zones. You can walk through South American rainforests, African savanna, East Asian subtropical regions, and Mexican deserts within this single section. The Susan Garver Family Discovery Garden features a boardwalk maze, lagoon, and water play areas with dams and pumps. The Culinary Garden grows plants you can develop at home for dinner. It also has an apothecary corner displaying herbs to heal. Walking trails extend over 2.5 miles through the grounds.

    Visitor Information

    The garden operates daily from 9 a.m. to 5 p.m.. Everyone 3 and older requires a ticket. The facility runs cashless for all transactions. Service animals accompany visitors, though other pets stay home. Food belongs in the picnic area rather than within gardens. Two water refill stations sit adjacent to restrooms in the Welcome Pavilion and Susan Garver Family Discovery Garden.

    Houston's Underground Tunnel System

    Overview

    A climate-controlled pedestrian network runs twenty feet below downtown streets and links 95 city blocks across approximately six miles of walkways. This tunnel system connects office towers, hotels, banks, restaurants and retail spaces. You never need to step outside. Houston's heat and humidity make street-level walking uncomfortable for much of the year. The underground route provides a practical alternative that office workers and visitors use often.

    Construction began in the 1930s as a passage between two movie theaters. The system expanded through the decades into one of the largest underground pedestrian networks in the United States. Most of the network occupies the western half of downtown. Passages run through building basements and connect via corridors.

    Highlights

    The tunnel houses gift shops, newsstands, banks, technology centers, flower shops, copy centers, dry cleaners and food courts similar to shopping mall offerings. These spaces fill with downtown employees on weekday lunch hours. They grab meals or run errands without facing outdoor weather.

    Visitor Information

    Access operates weekdays from 6:00 a.m. to 6:00 p.m.. Wells Fargo Plaza and McKinney Garage on Main Street provide the only direct street entry points. All other access points require you to enter connected buildings via street-level stairs, escalators or elevators. The system closes evenings and weekends, except tunnels that serve Theater District parking.

    Smither Park

    Overview

    More than 300 artists turned a half-acre plot into a public mosaic gallery where every surface tells a story through recycled materials. Smither Park occupies the corner where Third Ward meets East End, adjacent to The Orange Show monument. Visionary artist Dan Phillips worked with Stephanie Smither to design this space honoring her late husband John H. Smither, both longtime supporters of self-taught art. The park opened in September 2016 and functions as a living canvas where artists continue adding to the permanent collection.

    Highlights

    The 400-foot memory wall anchors the space with more than 50 panels. Different artists designed each panel using donated dishes and found objects. The Lindley Fish Amphitheater rises from the ground in the shape of its namesake and hosts live music one Sunday a month from 1 to 5 p.m. among craft activities and artisan vendors. A tower containing kinetic sculpture by Houston artist Smitty Regula stands among the Burguires, Hinton & Mathre Swings, the Vinson & Elkins Pavilion, and the Marilyn Oshman Meditation Garden. Artists work on-site Saturdays. You can watch mosaic pieces take shape.

    Visitor Information

    The park opens daily from dawn until dusk at 2441 Munger Street. Admission costs nothing. Programming expands beyond those Sundays with occasional festivals and performances throughout the year.

    Gerald D Hines Waterwall Park

    Overview

    A 64-foot semi-circular fountain stands before you, where 11,000 gallons of water cascade every minute. This creates one of Houston's most striking sensory experiences. Gerald D. Hines Waterwall Park occupies 2.77 acres south of Williams Tower in the Uptown business district. The fountain's height corresponds to the 64 stories of the adjacent tower. John Burgee Architects designed it with Philip Johnson as an architectural complement to the office building.

    The park is open daily from 9 a.m. to 8 p.m. The fountain recycles 46,500 gallons through its internal system every three hours and two minutes. Water flows down both the concave interior and convex exterior surfaces. This creates channeled sheets that visitors can view from multiple angles. The park surrounds this centerpiece with 186 live oak trees grown in Jacksonville, Florida, and a 360-foot lawn flanked by 11.5-foot-wide sidewalks.

    What to Experience

    Mist from cascading water envelops the viewing area. The constant roar of falling water accompanies it. You can walk the full perimeter and experience the fountain from both inside the semi-circle and from the exterior viewing areas. The structure uses St. Joe brick as its primary material, with Romanesque arches constructed from Indiana Buss limestone and a black granite base.

    Visitor Information

    Admission costs nothing. Williams Tower Visitor Parking Garage provides the most convenient parking access, though some parking locations may require payment.

    Conclusion

    Houston's appeal comes from variety rather than a single signature experience. You've seen attractions spanning space exploration and natural green spaces, along with underground passages designed for practical navigation. What matters most depends on how you prefer to spend your time. Museum visitors can move between free admission institutions and specialized collections within the same trip. Outdoor enthusiasts find enough parkland and waterways to fill multiple days. Houston's scale means grouping attractions by location saves you drive time between stops. The zoo and natural science museum both sit in Hermann Park. The Museum District concentrates multiple cultural institutions within walking distance. Plan around what you want to experience rather than checking boxes on a generic list.