The remains of an ancient Roman city are hidden underneath Bologna's beautiful public library.

Legend has it this fountain built to symbolize the Pope’s power hides a strange secret concerning Neptune's manliness.

A diverse collection of wax, bone, papier-maché and mummified relics.

Over 100 towers were built in Bologna during the Middle Ages, but only 22 survive.

In the world's oldest university is a stunning 17th century anatomical theater carved from spruce.

A small window on Via Piella offers a lovely and rare peek at Bologna's lost canals.

The mummified relic of St. Catherine sits forever on a golden throne.

A Nesting Doll of Churches.

Hidden beneath the famous St. Peter's Basilica is a veritable city of the dead that may hold the remains of St. Peter himself.

The final resting place of the poets Shelley and Keats.

The skull of the patron saint of lovers lies in the Basilica di Santa Maria in Cosmedin—maybe.

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

Rome's semi-secret peephole vista is also a former Crusader stronghold.

The underground sanctuary of a mysterious ancient cult.

A master of trompe-l'oeil creates a stunning, tourist-fooling dome out of a flat ceiling.

Hundreds of lucky felines haunt the ruins where Caesar was murdered.

An alchemist's "magic door" stands in the middle of a Roman park.

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