The prototype for all Nazi concentration camps.

The fairy tale castle of the “fairy-tale king,” this was also the inspiration for Disney’s “Sleeping Beauty.”

A peat bog in southern Sweden provides a cozy and photogenic home for junked Volvos, Saabs, and the occasional American muscle car.

The first recognized Neanderthal remains were found in this now-lost cave in 1856.

This "floating railway" is one of the world's oldest monorail systems.

The largest mosque in Germany.

Thousands of tourists and residents in Cologne affix "love padlocks" on the Hohenzollernbrücke Bridge to symbolize their affections.

The convergence of two currents makes this a surprisingly pleasant getaway in the Arctic Circle.

The great polar explorer is remembered in this far northern town, where he embarked on his final expedition.

The world's most charming instant portrait studio also happens to be its smallest.

This functioning parish church is also the site of many concert performances due to its wonderful acoustics.

The world's northernmost aquarium looks like it has fallen over.

Swedish skyscraper with a 90° twist.

This chimerical bridge/tunnel appears to dead end right into the sea.

This triumphal arch celebrating the Sun King's conquest of Lille is a masterpiece of military architecture.

The place to be if you love vintage Swedish cars.

This gem from the industrial age helps visitors and residents alike traverse hilly Stockholm.

This Stockholm light tower can be controlled by anyone with a smartphone.

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

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

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.

Berlin's old airport.

The bunker where Hitler took his own life is hidden under this deliberately ordinary parking lot.

Thousands of coffin-like pillars make up this controversial Holocaust memorial.