Nice tunnels, though I prefer mine with less guns. © Don Bartletti / LAT, 2007
On Border Tunnel Infill: an interesting writeup over at Subtopia about tunnels running under the border between the US and Mexico, used for the obvious purposes, and how they're too expensive to fill.
Seven of the largest tunnels discovered under the U.S.-Mexico border in recent years have yet to be filled. One of which is the longest yet found and extends nearly half a mile from San Diego to Tijuana. There’s another sophisticated passageway, he says, once known as the Taj Mahal of tunnels, which has been sitting unfilled for 13 years. Filling the seven tunnels would cost about $2.7 million, according to U.S. Customs and Border Protection officials.It's actually from a couple articles in the LA times, but I prefer the summary with photos interspersed. These tunnels are much nicer than the "drug smuggler tunnel" that some explorers recently dug in a US metropolis for fairly silly reasons.