Its collection includes a broad array of social, geographic, graphic design, and political history.

This unique architectural wonder is also tied to one of the 20th-century's most renowned writers.

This Industrial Age architectural and engineering gem helps visitors and residents alike traverse Lisbon, “The City of Seven Hills.”

A king's pet, a pope's gift, an artist's inspiration, and a tragic shipwreck.

A towering monument to war, located on a beautifully peaceful hill.

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

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

This mine is home to the largest man-made hole in Europe.

Macabre astrological automaton clock dating to the late 1400s.

This collection of over 50 murals celebrates Brussels' rich history as the self-proclaimed home of the "comic strip."

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

A little sculpture with a large wardrobe.

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

One of Amsterdam's narrowest houses is located right across the canal from its widest.

This basement museum explores the art and artistry of fascism.

Stockholm's decidedly unique public transit system has doubled as the world's longest art gallery for decades.

Stockholm's deepest subway station is also a stunning ecological wonder.

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

This doorless 20th-century elevator doesn't stop or slow down.

Looming communist pillar with a Czech twist.

A bust of Franz Kafka spins in pieces, reflecting the writer's inner torment.

A master of trompe-l'oeil creates a stunning, tourist-fooling dome out of a flat ceiling.

The yawning maw of this pagan visage is said to bite off the hands of liars.

One of the few remaining ancient aqueducts described by Frontinus as 'the most solemn testimony of the Empire.'