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

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

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

Three bridges and one giant canyon make up this fantastic Spanish settlement.

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

Dine at a legendary after-hours joint frequented by David Bowie and Iggy Pop.

This antique thermometer honors the creator of the first universal temperature scale.

A striking public sculpture representing the period of martial law in Communist Poland.

A 90-ton, gravity-defiant steam locomotive shoots for the skies in this bizarrely beautiful public artwork.

A huge wooden clock that is so beautiful its creator was forcibly blinded.

This imposing 20th-century castle was abandoned before it was ever completed.

A World War II torpedo launch station abandoned off the Polish coast.

Space-age monument to an early 20th-century uprising.

The discovery of an old wall led to the creation of this fascinating museum about the city in the Middle Ages.

An abandoned swimming pool decays on the outskirts of Berlin.

These former Nazi anti-aircraft towers offer a singular view of the north of Berlin in the summer, and a sanctuary for bats in winter.

Home to 10,000 medical specimens including the remains of Rudolf Virchow's extensive collection of pathological specimens.

The social hall of this former factory is a Communist-era time capsule.

Rebuilt several decades ago, its striking murals prevent it from being reconsecrated as a church.

The Grand Mall in Varna hosts one of the biggest collections of Soviet-era paraphernalia in Bulgaria.

Crossing a suspension bridge above a forest is the only way to reach this 12th-century monastery.

Not far from a popular beach, an unfinished, abandoned mansion for Bulgaria's last communist dictator.

These natural cliffs look like they are a part of an old castle complex.

When a conglomerate of visionary startups commandeer a disused Greek Orthodox Church, zaniness ensues.