This demon atop the Notre-Dame de Paris looks utterly bored.

This bridge was constructed from the rubble of the infamous Bastille.

In the best of all possible worlds, everyone will get a chance to see this statue in which Voltaire's heart is interred.

19th century pendulum and a clock restored by a rogue group of guerilla artists.

An early 20th-century bullring converted into a modern shopping center.

A vista of the city and sea from atop the little-known viewing deck on an unassuming Columbus statue.

The 2,000-year-old Roman columns are hidden within Barcelona's Gothic Quarter.

The largest Art Nouveau complex in the world is a Barcelona hospital with a 600-year-long history.

Mountain where Jesus was first tempted by the Devil.

150 or so scrounged-up lamps, chandeliers, and lanterns light up this alley in central Athens.

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.

This historic structure has been used as a mosque, a barracks, a prison, a school, and a bakery.

Preserved portions of Athens's ancient defenses are on display in a subterranean parking garage.

The oldest standing Byzantine church in Athens is tucked within a monastery in the middle of an upscale shopping district.

A Byzantine-era church hidden in a wooded area below the Acropolis.

Heralded as the world's first theater, these ruins are often overlooked as they reside in the shadows of the Acropolis.

The ruined doorway is a portal to the building's turbulent and torturous past.

The Cycladic architecture makes this Athens neighborhood feel like an island paradise hidden in the shadow of the Acropolis.

This small 16th-century church in Athens is almost entirely surrounded by a modern building.

Where commuters walk through remnants of an ancient Greek necropolis.

This 15th-century island fortress later served as home to the executioners no one wanted to live near.

An ancient octagonal weather station named for the eight Greek gods of wind.

This ancient Greek place of assembly and marketplace is being revealed layer by layer below the modern Athens cityscape.