More sculpture than building, this architecturally significant temple was built on the spot of Saint Peter's crucifixion.

A sulfuric hellscape in southern Italy.

This ancient Roman prison is decorated with an upside-down cross not as blasphemy but as saintly tribute.

A stunning cemetery famous for its extraordinarily delicate & lifelike mourning sculptures.

Secret refuge and museum of the Duke of Florence.

On rare days, this abandoned castle's gatekeepers open its doors, revealing the eye-popping splendor hidden inside.

An ancient artistic garden parlor full of hidden water wonders.

One of the largest caves in the world open to the public.

This real life asylum of horrors is now an abandoned ruin that hides the unbreakable code to one patient's insanity.

A dismembered holy head stares out from her beautiful reliquary at the St. Dominic Basilica.

The famous sculptor left his mark on this Italian wall in an internationally protected example of street art.

A hospital where antique dolls are given new life.

This half-finished "city of toys" was almost Italy's own Las Vegas.

The remains of a town so thoroughly destroyed by French forces that the citizens simply left.

Jesus' footprints and the first catacombs in the world.

This quaint Italian town keeps losing ground as the sides of its plateau slowly erode.

A sunken idol welcomes parishioners to Davy Jones' Locker.

A fairy tale castle in modern Rome.

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

A complex, nine-layer maze on the grounds of a Venetian doge's playground.

Pilgrimage site for star-crossed lovers.

Virgil's many-mouthed gateway to the underworld.

This immaculate and historic water garden culminates in a massive stone dining table with an inset fountain for chilling the wine of the Cardinal's guests.

The oldest operating pharmacy in the world features 800-year-old recipes.