These secluded and abandoned anti-aircraft defenses have become one the most scenic viewpoints in Barcelona.

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

Step inside the first house designed by Catalan architect Antoni Gaudí, considered to be one of the first Art Nouveau buildings.

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

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

A wonderfully kitsch bookstore the size of a supermarket.

Nature is slowly overtaking this disused cemetery on the outskirts of Brussels.

Climb inside an iron crystal magnified 165 billion times its normal size.

A little sculpture with a large wardrobe.

A horde of stray cats rule in this secluded Parisian cemetery under a bridge.

The water-powered carriages are long gone, but for over a century this funicular railway has been the fastest route to the highest point in Paris.

The vast, legendary catacombs hold secrets much stranger than stacked bones.

France's most famous cemetery, with some of its most curious tombs.

Dedicated to the history and culture of smoking, this small museum now includes a vape lounge.

This museum houses an imposing skeleton army comprised of creatures great and small.

Known as the "Dodo Manège," this carousel features a herd of animals that have disappeared—or may be gone soon.

The video game-themed street art first popped up in the French city.

Notorious artist squat renovated into legal studios.

An "inside out" building in the historical center of Paris, featuring Europe’s largest modern art museum.

This former insane asylum now holds a pathological anatomy museum.

A neo-Gothic church built to thank God for saving the Emperor of Austria from an assassination.

Macabre museum devoted to historical Viennese murders.

Built to give thanks for the passing of a plague epidemic, this cathedral is a one-of-a-kind architectural hybrid.

An exquisite Baroque church in Vienna's old town.