Underneath this Byzantinian church lies a necropolis filled with ancient tombs and the ruins of previous churches.

This building has two facades of clashing architectural designs.

A striking symbol of the Bulgarian capital.

"Unity, Creativity, Beauty."

This Slovak bridge is known both for its connection to a national uprising and its UFO-shaped eatery.

A sculpture of a beloved local figure, who tipped his top hat to everyone he passed on the streets of Bratislava.

This Slovakian statue of an emerging sewer worker might just be a bronze peeping tom.

This giant radio telescope would be a rusting ruin if it hadn't become such a beloved relic.

The facade of this 16th-century building is decorated with carvings of 300 seashells.

A Spanish artist builds his own castle.

The Roman city was the birthplace of various emperors and is home to one of the empire's most impressive architectural feats.

This centuries-old tower hosts endangered bald ibis mating pairs and looms over a pristine beach.

Dead weights honor the dead of Portugal's fishing industry.

At night, bats patrol this magnificent 18th-century space in search of book-eating pests.

This eccentrically decorated palace is replete with grottoes, fountains, tunnels, and caves.

An ancient and majestic fortress that played an integral role in Portugal's road to independence.

This unreal Portuguese palace looks as though it's made from a pile of different castles.

This huge abandoned fortress hidden inside a mountain holds a world of subterranean secrets.

One of the oldest and largest wooden churches in France was very evidently constructed by shipbuilders.

Ivy-covered Medieval tunnels cut through this charming town in France's Loire Valley.

A stunning 18th-century site where pilgrims ascend by a series of punishing stairs only to return via funicular.

Invisible bridge parts the waters, invoking biblical images and preserving the ominous feel of an ancient moat.

This ghost town in Belgium will lose its street art when it ceases to exist.

Take a leisurely walk through the park to find the seven giant troll sculptures hidden throughout the park.