Super-heavy Nazi architectural experiment.

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

This imposing modern citadel started out as a home renovation project.

An architect transformed this abandoned cement factory into his castle-like workshop.

A stately palace has been converted into the world's largest cannabis museum.

Bask in the 19th century grandeur of an eccentric Freemason millionaire's private gardens.

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

This semi-secret storybook hedge maze is also the oldest garden in the city.

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

A 12th-century fortress containing some of Berlin's oldest buildings.

A museum dedicated to the history of a terrifying secret police is now held in their former headquarters.

A century-old shot ball factory tower is open to the public once a year.

A tour of underground Berlin takes you through WWII air raid shelters and tunnels used to smuggle people out of East Germany.

Floating swimming pool within a moored vessel.

This water-tower-turned-high-end-apartment building was once the site of an early Nazi concentration camp.

Berlin's oldest surviving academic architecture hosted decades of animal dissections.

The most visited, and possibly most controversial, museum in Germany.

The largest free-standing aquarium in the world resides in a hotel lobby in Berlin.

A fascinating insight into daily life in the Eastern Bloc.

Beneath the impressive baroque cathedral that rises from the center of Berlin lies the largest collection of Prussian royals in the world.

Someone loved this song enough to carve all of its lyrics onto a tree trunk in a Berlin park.

A unique Holocaust memorial tells the personal stories of the Jewish residents exiled from greater Berlin.

After a nearly successful attempt on Hitler's life, the conspirators met their fate in the courtyard of this Berlin building.

This World War II bunker now survives as a documentation of the Nazi regime and war crimes.