This astonishingly geometric cave has inspired everyone from Jules Verne to Pink Floyd.

Modern art meets modern convenience in possibly the world's most architecturally important public bathroom.

A 2,000-year-old engineering wonder hides beneath an Italian town.

This underground museum highlights the history of Mexico City's subway system.

This recently restored crypt was once plagued by liquefying coffins and exploding caskets.

The burial place of an obscure North African saint was turned into a macabre body preservation factory for the 17th-century Neapolitan elite.

A trove of century-old litho stones from the Puck Building's printing days were discovered behind a cellar wall, and are now hanging in the store.

Historical figures from New York City's Catholic community reside in Midtown.

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

A rather vulgar example of the transition from Latin to the Italian vernacular.

The former home of an Italian artist is now a shrine to his ambitious works.

A huge enchanting public park just outside the ancient walls of Rome.

Brass cobblestones mark the places where individual Holocaust victims were taken from their homes.

The spot where the fascist dictator made some of his most famous speeches including declaring war on Britain and France.

Roman-era ships unearthed...

A modern sliver of architecture in Roma.

This beautiful park on the outskirts of Rome protects the ruins of two colossal ancient aqueducts.

An Italian ghost town that fought obscurity, until a mysterious illness brought it to its knees.

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

This hill made entirely of ancient Roman jars was simply a garbage dump to the people of the time.

Museum dedicated to literary greats of the Romantic Period is also the home in which Keats met his untimely end.

This delightful little museum is dedicated to only one thing: pasta.

The Pope’s secret escape route.

The martyr's wax-enhanced skeletal remains lie preserved in a glass case in the Santa Maria della Vittoria in Rome.