This is the oldest Roman-made bridge in the city still existing in its original state.

A modern sliver of architecture in Roma.

The Pope’s secret escape route.

This hidden Art Nouveau courtyard is an opulent feast for the eyes.

A burial vault located under Tiber Island in the middle of the Italian capital.

This hydrochronometer was invented by a Dominican monk and is a prime feature in this garden.

Jesus' footprints and the first catacombs in the world.

The skull of the patron saint of lovers lies in the Basilica di Santa Maria in Cosmedin—maybe.

The yawning maw of this pagan visage is said to bite off the hands of liars.

The crypts of Capuchin friars decorated with the bones of over 4,000 friars, including an entire "crypt of pelvises."

Perfectly preserved ancient monastery in an impossibly dramatic location on a rocky island in the Atlantic.

This remote British Imperial telegraph relay outpost drove men insane.

The United Arab Emirates's biggest and oldest fort pays homage to a lost era.

An abandoned desert hamlet swallowed up by sand.

Under the right circumstances, this waterfall in Yosemite briefly turns a luminescent fiery orange.

An exquisite tunnel of cascading flowers.

Twice a day a speeding train passes only inches from the homes of this residential neighborhood.

The largest pool at its elevation sits on top of one of the most expensive resorts in the world.

A maze of crosses marks the jumbled divide between the Netherlands and Belgium.

The world's highest and most dangerous infinity pool lies at the precipice of Victoria Falls.

Despite many attempts to finish this overpass, it has been abandoned since the 1970s.

The only museum with its curator—and her pets—buried inside.

A sinister pyramid in the Frari contains the heart of the famous neoclassical sculptor.

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