Project Faultless Atomic Explosion Site
Warm Springs, Nevada
In the 1960s Las Vegas began complaining that underground atomic explosions at the nearby Nevada Test Site were jiggling their casinos (which was bad for the roulette wheels and craps tables).
The U.S. military, always sensitive to the needs of its Sin City neighbor, opened a second Nevada Test Site further away from Las Vegas, detonating a one-megaton nuke a mile underground on January 19, 1968. Unfortunately the explosion created a shallow crater of about 4,000 square feet. This upset the local population even more than the casino owners, and all further tests were canceled. The shaft was plugged, creating an unintentional "monument" on which a memorial plaque was later affixed. It also warns against any digging, or taking away any dirt or rocks for souvenirs.