The Houston tunnel system is a network of subterranean, climate-controlled, pedestrian walkways that links 95 full city blocks below Houston's downtown streets. It is approximately long. There are similar systems in Chicago, Dallas, Oklahoma City, Montreal and Toronto. The first link was built in the 1930s by Ross Sterling to connect two neighboring buildings he owned, inspired by the tunnel system at Rockefeller Plaza in New York City. Soon after, Will Horwitz, an entertainment entrepreneur, connected three of his vaudeville and movie theaters to save on air-conditioning. Architectural historian Stephen Fox has stated that the idea for the tunnel system came when the Bank of the Southwest Building was "linked by tunnel to the 1010 Garage and the Mellie Esperson Building" in 1961.