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

Following the trail of an old metro line, this scenic path is haunted by a creepy spriggan statue.

The largest of London's subterranean rivers and once a mad, bad center of London life.

One of the few remaining casualties of the London Blitz, this destroyed church has become an enchanting public garden.

Abandoned railway line circling the city of Paris.

Walk upon the mementos of the dead in this Parisian courtyard paved with medieval tombstones.

A mechanized clock where a man fights off a dragon, crab, and rooster.

A hospital closed seemingly in the middle of operations, leaving behind fodder for horror films and ghost hunters.

Trails through lava-carved tube-caves display sparkling bacteria and a rich history.

A trash dump made beautiful by nature's power.

Exotic feline breeding compound and conservation center.

This unlicensed collection of fast-food memorabilia sits on the site of the first ever McDonald's restaurant.

Medical and zoological curiosities for sale.

Behind this beachfront shop lies a spectacular, colorful sea cave with an equally colorful past.

An unfortunate geological resemblance to Satan has labeled this Pasadena gorge as a passage to the underworld.

The vast, legendary catacombs hold secrets much stranger than stacked bones.

Resting place of Hollywood's immortals is also site of summer film screenings.

Non-profit time travel mart sells goods you would need for a trip through the fourth dimension.

This iconic L.A. bookshop is housed in an abandoned bank—both symbolic and chic.

The abandoned zoo enclosures offer a perfect place to experience the other side of the bars.

An underground city of salt.

Real bones which are said to have belonged to a Polish dragon.

This astonishingly geometric cave has inspired everyone from Jules Verne to Pink Floyd.

The one-time watch house for incoming ships at the Golden Gate now stands abandoned and hidden in trees.