Renowned mathematician and physicist Carl Friedrich Gauss once worked at this observatory.

This giant, 83-year-old ship elevator is an engineering feat to behold.

Climb a steep hill in 90 seconds on the second-oldest urban subway in the world.

An historic and oft-filmed spot for musclebound iron pumpers on the Pacific coast.

A little sculpture with a large wardrobe.

Four glass boxes hover over 1,000 feet in the air to give visitors an unparalleled view of Chicago.

Hollywood's most famous landmark, the "temporary" sign that has stood for decades longer than intended.

France's most famous cemetery, with some of its most curious tombs.

The celebrated eyesore created by starry-eyed sweethearts.

Kings Cross Station pays tribute to its role in Britain's best-selling book series.

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

In all of the 29 years it was in operation, no prisoners ever escaped successfully... or so they claim.

London's creepiest cemetery was once the site of dueling magicians and mobs of stake-carrying vampire hunters.

A rooftop restaurant hides in plain sight atop Vienna's Palace of Justice.

Austria's very first and only nuclear power station was completed but never used.

The world's largest historic armory was established by independent citizens to defend themselves from the wars of larger forces.

Austria's ultra-modern art museum looks like Cthulhu's giant alien heart.

Apartment complexes built into huge repurposed natural gas tanks.

Resting in the middle of an Austrian river, this sci-fi "island" lets people cross in neon style.

The shell of a medieval fortress offers commanding views of the area it once protected.

American soldiers discovered Europe's best one-liner at the end of World War II.

Ride a dragon train into a world of dwarves.

Beautiful Austrian natural history museum with carved ceilings and row after row of ancient taxidermy.

Baroque celebration of the end of the Great Plague of Vienna.