This elegant Colombian fortress was one of the torture headquarters for the Spanish Inquisition.

The caldera of this mini-volcano has been turned into a naturally heated mud bath.

The "Greatest Sewer" of ancient Rome is one of the oldest sewer systems in the world, and is still in use.

This bronze boar's snout has been rubbed to a golden sheen by visitors seeking good fortune.

This memorial was raised in honor of a group of workers heavily impacted by the 1985 Mexico City earthquake.

This Mexico City subway station will make you feel like you've been transported to the London Underground.

It's believed this golden brick is part of the legendary lost Aztec treasure.

Once home to an aristocratic family and a workers' organization, this intricately tiled building now houses a chain restaurant.

This ancient structure was built by a mysterious civilization that was largely destroyed by a volcanic eruption.

This colossal ancient sculpture of the monstrous Aztec rain god has a literally stormy history.

Mexico City's largest market contains a Willy Wonka-esque wonderland.

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

A colorful "forest" made entirely from three tons of recycled plastic waste.

This Japanese-inspired park showcases the city's peculiar trends for naming features after foreign rulers.

This museum dedicated to cartography is housed in a former 17th-century convent.

A bronze statue of the famed Prussian naturalist commemorates the year he spent in Mexico.

Its most enigmatic sculpture is a giantess with a ghostly face on her knee.

A fabulously bizarre surrealist sculpture by the late artist Leonora Carrington.

The unique collection of gifts includes braids of human hair, a spoon, and a Virgin made of bread.

The burial place of some of Mexico's most prominent residents is full of macabre stories and hidden masonic symbols.

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

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

A church dedicated to the Mexican skeleton saint.

The famous artist couple lived and worked here, in two different houses separated by a bridge.