The Houston Tunnel System is a network of climate-controlled, pedestrian walkways, 20 feet below Houston's downtown streets. It links 95 city blocks and connects office towers to hotels, banks, restaurants, stores, and the Houston Theater District.  
The tunnels are approximately 6 miles long. The first one was built in the 1930s by the governor of Texas, Ron Sterling, because he wanted to connect two of the buildings he owned.
Most of the tunnels are not owned by the city. Each building is privately owned and spaces are leased. Only Wells Fargo Plaza and Mckinney Garage on Main offer direct access from the streets of the tunnels. Otherwise, entry points are located inside office buildings. The Tunnel System is open on weekdays from 6:00 am to 6:00 pm.