In all of the 29 years it was in operation, no prisoners ever escaped successfully... or so they claim.

The beautiful tunnel that ran from the lobby to Penn Station is still hidden underneath 34th Street.

You feel like you're in a forest, but you're actually walking amidst the branches and trunks of a single giant tree.

This stunning Brazilian library contains the largest collection of Portuguese texts outside of Portugal itself.

The only visible remains of this ancient Greek underground temple is its roof protruding from the earth.

These hut foundations are believed to be the residence of Romulus, founder of Rome.

An ancient Roman temple first dedicated to an emperor's wife is now a church.

This small, ancient Roman temple was once a church dedicated to the patron saint of penitents.

The ruins of this Roman temple dominate the small city in southern Lazio.

A popular legend claims that the famous pizza was invented at a restaurant in this alley.

The walls and streets of the ancient city are peppered with penises.

Ancient snack bar of the Roman Empire re-opened.

Erotic art covers the walls of the largest ancient pleasure palace.

An underground paleo-Christian burial site composed of the remains of several cemeteries and Basilicas.

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

This medieval Italian town is a sheer (and beautiful) cliffside defense.

Crushed coral and crystals give the sand its signature coloration.

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

The doodles of a genius line the walls of a secret room under the Medici Chapel, where they were hidden for nearly 500 years.

Thousands of well-dressed mummies below a monastery.

The last moments of the ill-fated Pompeiians, frozen forever in plaster.

Pompeii's less famous neighbor is still revealing her secrets.

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

A rare example of a medieval house in Rome adorned with a melancholic inscription.