"Holy Wisdom" overlooks the city that became its namesake.

Now abandoned, the world's first torpedo factory is crumbling into the sea.

This shining multicolored metro station deep under Naples is said to be the most beautiful in Europe.

These "anatomical machines" are only one of the many strange items in this Italian crypt.

Architectural monsters are devouring this palace's every door and window.

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

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

This equestrian statue of Constantine the Great has been the subject of criticism for centuries.

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

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

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

This Venice bookstore has resigned itself to constant flooding by keeping its books in bathtubs and boats.