This historic Amsterdam bar used to accept sailor's monkeys as payment.

This gorgeous reading room houses the oldest and largest art history library in the Netherlands.

This city square is home to Amsterdam's oldest church and a statue honoring Dutch sex workers.

This impressive collection of rare books on ancient mysticism inspired author Dan Brown.

Three connected pink triangles memorialize persecuted gays and lesbians throughout history.

An Amsterdam street lined with antique shops each one dedicated to a different obscure collection.

In the days before house numbers, these colorful signs held clues about various buildings' purposes.

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

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

The site of the famous Nazi book burning campaign of 1933 remembers its "Night of Shame".

The world's first clock to use set theory as a measure of time required the invention of a new light bulb just to maintain its obtuse measurements.

A monument to the three wars that led to German unification towers within a Berlin traffic circle.

One of the world's heaviest musical instruments towers within a popular urban park.

Metro station with a claim to rock n' roll fame.

Tiny memorials honor individual victims of the Holocaust.

Cold war icon and onetime "hole" in the iron curtain.

A fascinating insight into daily life in the Eastern Bloc.

On the Spree bank, discover one of the last reminders of a symbolic wall that divided, and was torn down by the people.

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

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

This futuristic German spa allows visitors to float in a pool of salt water while zoning out to underwater techno.

This automated sculpture of two men peeing will spell out text messages with their micturition.

The history of occult science is turned into a creepshow at this lurid Prague tourist attraction.

Two stunning 17th-century libraries and a cabinet of curiosities.