Houston, in the summer, can be really hot and humid. The Houston tunnel system offers pedestrians a network of subterranean, climate-controlled walkways that links 95 full city blocks 20 feet below Houston's downtown streets. The Tunnel system links office towers to hotels, banks, corporate and government offices, restaurants, retail stores, and the Houston Theater District. Portions of the tunnel contain gift shops, newsstands, banks, technology centers, flower shops, copy centers, dry cleaners, and food courts similar to a major shopping mall. They are widely and heavily used by office workers and tourists. There are sections of the tunnel system labeled yellow, red and green designating area of the tunnel system.