World's first "penitentiary," meant to be humane, drove men insane.

Moonbows over Kentucky.

One of the longest wooden benches in the world snakes around Geneva's Treille Promenade.

Unable to build support structures on glaciers, the engineers for this tramway were forced to design a unique system.

Enormous lake at the bottom of a unique cave system.

A bizarre roadside attraction and the first instance of miniature golf in the world.

Once decrepit and slated for demolition, now one of the longest pedestrian bridges in the world.

The highest point in Tennessee, Clingmans Dome bears witness to the ravages of one type of insect.

Mile-long cave system near Great Smoky Mountains.

The secret city built by the Manhattan Project.

Better known as the "Body Farm," this unique research facility has been studying how human bodies break down since the 1980s.