Jail from the 19th century that was built by inmates.

Where Stoddart and Connolly suffered in the infamous Bug Pit.

A scenic fort on the harbor protected Philadelphia from an attack that never came.

Structure built from the skulls of vanquished foes.

Burial grounds for more than 1,000 bodies deep under the modern town of Rabat.

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

Jesus' footprints and the first catacombs in the world.

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

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

Crypt mausoleum in cathedral's basement contains relics of third century Roman martyr, Saint Vibiana.

A former top secret nuclear fallout shelter now operates like a hotel stuck in the Cold War.

Europe's second largest ossuary wasn't discovered until 2001.

A church of bones, decorated with 40,000 human skeletons.

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

This ancient village and its adjoining cemetery have a beautiful history of death and remembrance.

The crypts of Capuchin friars decorated with the bones of over 4,000 friars, including an entire "crypt of pelvises."

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

Plundered and left asunder by grave robbers, this ancient necropolis has been painstakingly pieced back together.

An absolutely beautiful 200-foot stained glass installation traces the evolution of knowledge.

Members of Congress have traveled between the buildings on Capitol Hill for a century hidden from tourists, press, and storm clouds.

A dilapidated psychiatric facility on the outskirts of Milan where electroconvulsive therapy was developed and Napoleon once lived.

This rustic cabin, outfitted with gun slits, was once home to John D. Tewksbury, patriarch of the bloodiest family feud in American history.