Gilded heaven for philatelists and architecture freaks, still in full working order despite sitting atop tremulous ground.

Visiting this cacophonous collection of vintage novelties is like stepping into the mind of a crazed toymaker.

A disquieting Aztec sculpture displays hundreds of stone skulls representing the victims of human sacrifice.

Explore the atmospheric ruins of an abandoned convent in the dense forests of Mexico's first national park.

Meant to be one of the most extravagant hotels in the world, now an eerie, abandoned architectural gem in Mexico City.

Twelve natural mummies are displayed in the crypt of this former monastery school.

A church dedicated to the Mexican skeleton saint.

66,000 pieces of art, donated by one of the world's richest men.

A jaw-dropping "megalibrary" that turns book-browsing into a geometric adventure.

Part bookstore, part café, and part forest.

Hidden away in a modern library are the remains of one of the 18th century's most celebrated wunderkammers.

A spectacular Petrine Baroque summer palace commissioned for Catherine I by Peter the Great.

These gutted monastery ruins still stand proudly in the middle of the Italian countryside.

These medieval skyscrapers dominate the skyline of this small Tuscan town.

A dismembered holy head stares out from her beautiful reliquary at the St. Dominic Basilica.

Next to the Leaning Tower of Pisa is a cemetery home to ancient sarcophagi and disturbing murals.

A local student's chance encounter with Keith Haring led to the creation of one of Europe's largest murals.

A coin-operated washing machine turned jukebox, complete with an outdoor dance floor.

Abandoned railway line circling the city of Paris.

This old wooden funicular railway leads to a cemetery in the forest.

An old slaughterhouse now holds the largest collection of pig artifacts.

A unique sculpture calls the outside of this steakhouse home.

Two old windmills got a new life as oversized sculptures of a man and a woman.

An abandoned textile factory on the "island of crows" was home to Estonia's first workers' strike.