The best preserved Paleochristian basilica in Rome hides a number of oddities and secrets.

Crumbling ruins of the thermal baths that once attracted royals and aristocrats from throughout Europe.

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

One of the most important yet well-hidden museums dedicated to the history of medicine.

St. Francesca Romana, patron saint of drivers, resides in the church she founded.

A treasure trove of Renaissance-era funerary art in a Roman church built on top of Nero's grave.

This mosaic-lined medieval church was built by the world's first admiral and still holds mass in ancient Greek.

These delicate sand pyramids look like naturally occurring gothic spires.

This abandoned island off the Venetian coast has been a radical monastery, a political prison, and a secret Nazi base.

A domed disco abandoned since the '70s now attracts artists and explorers under its unique roof.

Small on the outside, big on the inside, this church is an astonishing act of visual deception.

The mummified relic of St. Antoninus.

Europe’s oldest natural human mummy.

The studio built by fascists in the hopes of "reviving the film industry" with the occasional propaganda film opportunity thrown in.

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

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

An ancient artistic garden parlor full of hidden water wonders.

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

This Tuscan lake hides a 13th century town that is still visible when the water recedes.

Secret refuge and museum of the Duke of Florence.

Romans built the world's tallest artificial waterfall in 271 BC.

The astonishing collection of an infamous criminologist.

Dug as a secret royal escape route, the tunnel became a wartime bomb shelter and dumping ground for vintage cars.

Where Aleister Crowley taught magick in "La Chambre Des Cauchemars," his "Chamber of Nightmares."