Houston Urban Adventures, Houston

Houston Urban Adventures maintains that if you're looking for wonders, one of the best ways to find it is to search for buried treasure. On their signature Heart of the Tunnel walks, customers explore seven miles of air-conditioned tunnels, learning the history of the city through its art and architecture before venturing above ground to the top of the tallest building in Texas. Of course, not every treasure is hidden indoors—the Historic Downtown Pub Crawl whisks participants to a 19th-century gambling parlor, a tailor shop that moonlights as a watering hole, and the historic Market Square Park.