These millipedes glow not out of attraction, but as a not-too-subtle warning.

The last moments of the ill-fated Pompeiians, frozen forever in plaster.

Part modern art project, part traditional chapel, this see-through church is only substantial from the right angle.

This massive subterranean fissure is known as the "underground Grand Canyon."

The 953 windows undoubtedly make this the world's most beautiful screened porch.

Paris' fabled purveyor of exotic taxidermy and natural history curios.

The longest hedge maze in the world.

Dig for your own trilobites in this goldmine of invertebrates.

Ride the subways of yesteryear.

A haunting collection of the vanished and disappearing natural world.

The only swimming pool listed on the National Register of Historic Places is emptied and refilled each day with naturally filtered water.

The second-largest cave chamber in the world was discovered in 1898 by a 16-year-old and a friend known as "Pothead."

World's largest cave was only discovered in 1991, and now offers tours to the public.

Here, at the "world's longest art gallery," you'll find forty miles of ancient petroglyphs and pictographs.

This giant boulder is pinched over a 1000-meter abyss by two mountains.

A sculptor's dream castle turned fantastical ruin.

An encyclopedic collection of mammal penises.

A museum of carnival attractions where you are invited to ride the rides.

Iceland's largest lagoon is home to stunning multi-colored icebergs.

Treehouse motel and treehouse-building school.

This French ghost town from World War II has been left as a memorial to German atrocities during World War II.

Renaissance villa and gardens complete with a tormented colossus.

Hundreds of lucky felines haunt the ruins where Caesar was murdered.

Whisper secrets in a busy station only to be heard on the other side of this acoustic arch.