Secret refuge and museum of the Duke of Florence.

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

This one-of-a-kind Roman arch is not actually dedicated to the god Janus.

The ruins of the largest gladiatorial school in Rome are largely hidden under modern streets.

The best preserved Paleochristian basilica in Rome hides a number of oddities and secrets.

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.

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

Over 12,000 hygiene oriented objects and exhibits.

Tourists often confuse this beautifully ornate former cigarette factory for a mosque.

The largest treasure hoard in Europe is contained in a castle that was bombed out during World War II.

This Dresden church was purposely rebuilt Protestant after being demolished in World War II.

When the rain falls, this drain system turns into a musical instrument.

The stunning interior of this Gothic church is covered in ornate gold details.

Elaborate tile work in this railway station tells the story of Portugal.

A hidden three-foot-wide house separates these two regal churches.

Elaborately carved to showcase the glorious wealth that the age of exploration brought to the Portuguese empire.

A king's pet, a pope's gift, an artist's inspiration, and a tragic shipwreck.

Mountain where Jesus was first tempted by the Devil.

Gaudí's famously flamboyant architectural style is on full display in this sprawling park and garden.

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.

What looks like a suicide in progress is actually a statue of Sigmund Freud.

This tipsy office building in downtown Prague was originally called “Fred and Ginger.”