The Pope’s secret escape route.

A Nesting Doll of Churches.

Architectureal fantasy quarter of Rome.

This former Roman Catholic Church still contains the embalmed hearts and organs of 22 popes.

In Rome’s Jewish ghetto, a 200-year-old bakery still makes the neighborhood’s historic sweets.

An Aztec temple, the largest man-made pyramid in the world, sits buried in earth with a Spanish church set on top.

A display of torture devices used in the Spanish Inquisition and other scourges of medieval Europe.

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.

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.

An ancient ossuary in Rouen.

Charnel house at the foot of Mount Sinai.

Artfully arranged bones of 5,800 Austrians.

The personal charnel house of Anton Bruckner.

Mysterious painted skulls in Moravia.

Skeletons dressed in extravagant 18th century royal costumes cavort in the aisles of this German basilica.

The mortal remains of an estimated 70,000 people lie in the basement of a monastery in Lima, Peru.

The remains of 40,000 humans, meticulously stacked in a tiny churchyard shed.

One of the largest ossuaries in Spain is packed from floor to ceiling with bones.

This Peruvian bone silo lined with hanging human skeletons and hundreds of skulls is topped with a remarkable Michelangelo replica.