Houston skyscrapers used to lower their air pressure to pull free A/C from their neighbors. (citation needed, can't track one down quickly). But, it's a huge sy

Houston skyscrapers used to lower their air pressure to pull free A/C from their neighbors. (citation needed, can't track one down quickly). But, it's a huge system, approximately seven miles long[4]. 0. https://en.wikipedia.org/wiki/Houston_tunnel_system https://en.wikipedia.org/wiki/Houston_tunnel_system 1. Pictures: https://www.google.com/search?q=houston+tunnels+system https://www.google.com/search?q=houston+tunnels+system 2. NY Times article: http://www.nytimes.com/2007/08/21/us/21tunnel.html?_r=1&adxnnl=1&oref=slogin&adxnnlx=1201964533-giDOI7EQDa42VtvtwDFuEg http://www.nytimes.com/2007/08/21/us/21tunnel.html?_r=1&adxn... Startups have launched in the Houston tunnels: 3. http://www.chron.com/business/article/Downtown-tunnel-system-still-drawing-entrepreneurs-1736690.php#page-2 http://www.chron.com/business/article/Downtown-tunnel-system... Eye-popping costs of up to $15,000 per linear foot to build, and yet it's all funded by the building developers themselves: 4. https://web.archive.org/web/20081231041758/http://www.discoverhoustontours.com/Welcome%20to%20the%20Downtown%20Houston%20Tunnel%20System%20020722.htm https://web.archive.org/web/20081231041758/http://www.discov... (Out of all large cities in America, Houston is unique in that it has no zoning; skyscrapers are clustered together mostly because they're lonely, and not at all because there are inherent advantages in being near other like-minded buildings. The weirdest photographs to come from no zoning laws, which I think is actually extremely cool: http://www.chron.com/news/houston-texas/houston/article/Weirdest-images-from-Houston-s-lack-of-zoning-laws-9171688.php#photo-10795066 http://www.chron.com/news/houston-texas/houston/article/Weir... )