A beautiful but toxic fountain of mercury.

One of Antoni Gaudí's most classic buildings is well-known for its "dragon-back" design.

Construction of Barcelona's iconic (but controversial) church is expected to be completed in 2026—a century after the death of its architect.

A once grand hotel now sits eerily abandoned in the Catalan countryside outside Barcelona.

The mystic whose incorrupt corpse still attracts the faithful.

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

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

Rome's semi-secret peephole vista is also a former Crusader stronghold.

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

2300-year-old Roman road connecting the empire.

Jesus' footprints and the first catacombs in the world.

This ancient market is often referred to as the oldest shopping mall in the world.

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

This ritzy Italian market is built around a statue of an unforgiven heretic who was burned for his belief in an endless universe.

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

A Nesting Doll of Churches.

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

An alchemist's "magic door" stands in the middle of a Roman park.

Also known as the Square Colosseum, this building is a prime example of fascist-era rationalist architecture.

The only "Egyptian" pyramid in Europe and the legendary tomb of Remus.

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

A detailed pachyderm supports Rome's smallest Egyptian obelisk.

Thousands of abandoned statues of deities are taken to this hillside in southern Hong Kong.

Take a cruise with no movement but plenty of style in this one-of-a-kind boat mall.