The walls and ceiling of this Polish church are decorated with thousands of skulls, with another 21,000 skeletons just below.

Mexico's astounding mummy museum with "the world's smallest mummy."

This restored opera house is named after a soprano known for tragic romance, exile, and a truly uncomfortable wedding.

A graceful natural rock formation stands astride the point where the Gulf of California meets the Pacific Ocean.

The enigmatic and seldom visited ruins of a Mayan city-state.

The masses at this church incorporate enough moonshine and animal sacrifice that they are no longer recognizably Catholic.

From Nunavut to Tierra del Fuego, you won't find any lighthouse higher than this one.

Hotel designed around a 16th century Mexican bullring.

The stoutest tree in the world.

A neo-Gothic temple in central Mexico featuring a labyrinthine network of crypts.

A Mexican Romeo-and-Juliet-esque legend has given this super-narrow alleyway a reputation for romance.

The winter home of millions of migrating monarch butterflies.

A fairy garden in an old hotel hidden in La Marquesa forest.

High atop a Mexican rainforest mountain, this ancient pyramid once drew pilgrims countries away.

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

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

Frida Kahlo's childhood home, now a museum of her life and works.

An island filled with hundreds of hanging, decomposing, decapitated dolls.

A museum in the former home of Marxist revolutionary Leon Trotsky.

Part bookstore, part café, and part forest.

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

The only castle in North America to ever house European sovereigns.

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

This crumbling Art Deco movie palace in Mexico City has been abandoned for two decades.