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.

The Roman Emperor's lost summer home and grotto full of enormous sculptures sit along the Italian seashore.

Virgil's many-mouthed gateway to the underworld.

This picturesque Umbrian city has a subterranean side that has long remained hidden.

Inside this McDonald's you can dine on your Big Mac and fries next to a 2,500-year-old Roman wall.

A sunken idol welcomes parishioners to Davy Jones' Locker.

Dramatic sea stacks adorn the coast of this small village on the Adriatic coast.

Eco-village hidden in the foothills of the Alps that created a massive system of psychedelic underground temples.

Filled with goldfish swimming in a shallow pool of sea water, this ancient crypt is more wishing well than burial site.

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.

One of the world’s smallest bars, just 13 square feet, is brimming with speakeasy flair.

Abandoned medieval hill town.

Skulls from the plague of 1656 and World War II bombings are united by a cult dedicated to caring for the ancient dead.

Crushed coral and crystals give the sand its signature coloration.

This domed temple was built in a hidden cave mouth as a refuge for sinners seeking absolution.

A Milanese café entirely designed by the American director Wes Anderson.

The once forbidden "secret cabinet" of erotic art from excavations of Pompeii and Herculaneum.

Over 50 exquisite hand-painted Renaissance maps decorate a Medici storage room.

This centuries-old Italian chapel hangs midway down a sheer cliffside.

This 16th-century monastery has been turned into a surrealist architecture compound.

A labyrinth of ancient tunnels hidden below the city holds the ruins of 2,500 years of history.

An Italian hillside ghost town.

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