Hidden beneath the streets of London is a secret subway that only carried mail.

Trick water gardens from 1619 featuring a 200 piece mechanical theater powered by water.

An abandoned mine now resembles a post-apocalyptic landscape of derelict buildings and blood-red pools of water.

The first presidential bomb shelter was located in an old vault under the Treasury, connected to the White House via tunnel.

The preserved arm of a third-century sorcerer is believed to have the power to lift curses and spells.

A subterranean shelter remains intact under a busy Paris railway station.

A local dialect born in the late 19th century is only spoken in this isolated California valley.

A scandalous Art Nouveau collaboration that set Paris all atwitter at the turn of the century.

Crumbling remnant of Rio's colonial past tucked behind Corcovado mountain in the neighborhood of Cosme Velho.

Nature took her revenge on the "Wickedest City in the World."

The topiary maze at the Habsburg hunting lodge.

Dr. Strangelove-esque tours reveal the inside a bunker once reserved for Stalin himself.

This German version of Universal Studios holds a vault of treasures from the NeverEnding Story.

This stunning, out-of-the-way Croatian monument commemorates a community's uprising against occupying fascist forces.

Budapest's Communist-era statues, banished to the suburbs.

Cold storage for agricultural biodiversity.

Despite attempts by local police to discourage it, Beatles-inspired graffiti has been a means for artists to air grievances for decades.

Shelves covered in dozens of coffee bean varieties fill this North End institution.

A whimsical bridge adorned with decorative dragons.

This small primate research island is teeming with playing, fighting wild monkeys.

An enormous, 30-story-deep hole in the middle of Guatemala City.

An 18th century wonder of the world, lost in WWII, re-created at the Catherine Palace.

Unique antiquarian shop specializing in globes, maps, and prints.

Rusting ships sit in a desert where a sea used to be.