An unusual "skull with ears" sits in the crypt of this small church tucked away at the end of a narrow alley.

A rotating cast of guys and dolls in front of a Washington, D.C. building.

Underground monastery and fortress.

This Italian foot path winds through the mountains via 52 individual tunnels.

A century-long search for a church that was never there.

Abandoned for decades, trains still pass through the now-restored remains of one of Madrid's first metro stations.

This funky former tobacco factory is one of the most striking examples of Madrid's cultural diversity.

The oldest restaurant in the world is this old-world Spanish eatery, still known for its suckling pig.

The site of the climactic scene from the classic horror film is now a historic landmark.

Mother Nature outdoes herself with this stunningly beautiful set of caves carved into marble.

The mysterious "Candelabra of the Andes" could represent anything from a god's trident to a hallucinogenic plant.

The hermits of Karoulia protect their asocial lifestyles by living on the vertical face of a treacherous precipice.

High atop the Eiffel Tower is a small apartment built exclusively to entertain the science elite and make the rest of Paris jealous.

An Icelandic island full of diving birds and legend.

A haunting statue called "Eternal Silence" has quite the reputation among visitors with active imaginations.

The alpine falls where Sherlock Holmes apparently met his demise can actually be visited.

Hear the quietest sound from across the dome.

This Prague museum collects brutalist relics and memories from the country's former Soviet rule.

Bring your own cardboard to the slippery slopes of concrete hidden in a neighborhood park.

A former major munitions plant that has been converted into a sprawling art space.

Approximately 250,000 people left homeless by the great earthquake and fires found shelter in Golden Gate Park.

The Icelandic Sea Monster Museum explores the area's history of aquatic cryptid sightings.

This (occupied) house is 10 feet wide and full of spite.

A decaying concrete oil tanker served as a disposal location for bootleg hootch.