Small on the outside, big on the inside, this church is an astonishing act of visual deception.

This recently restored crypt was once plagued by liquefying coffins and exploding caskets.

Every equinox this Maya pyramid puts on a spooky ancient light show.

No telescopes, no power, no gift shop: The Observatory of Chichen Itza, one of the world's oldest observatories, takes astronomy back to basics.

A magical sinkhole on the Yucatán Peninsula is adorned with mini waterfalls and hanging vines.

This miniature take on the Kremlin is one Dutch man's retirement project.

A surrealist timepiece by the artist of melting clocks.

The recovered bones of martyrs slaughtered during The Terror are on display in this church crypt.

Mummified monks and the accidentally interred, in a 17th-century crypt.

The crypt of the imposing Stephensdom holds royal intestines and thousands of skeletons.

These 17th-century mummies are no longer naturally preserved, but remain on display today.

Jesus' footprints and the first catacombs in the world.

At the crypt of St. Mary of Eulogies and the Dead you are left alone to ponder mortality among piles of skulls.

This Italian pyramid is said to hold the mingled remains of the dead from both sides of the Battle of Novara.

This small chapel is built of human bones and decorated with a golden skeleton.

This modern French ossuary contains the jumbled bones of 130,000 WWI soldiers.

A 16th century chapel decorated with bones, skulls, and entire bodies hanging from the wall.

An ancient ossuary in Rouen.

Charnel house at the foot of Mount Sinai.

5,000 skulls in memorial to those killed by the Khmer Rouge.

Artfully arranged bones of 5,800 Austrians.

The personal charnel house of Anton Bruckner.

Mysterious painted skulls in Moravia.

Thousands of well-dressed mummies below a monastery.