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.

Dress up like a miner and take a slide into the disco-lit depths of this once foundational salt mine.

These bronze pamphlets remember a remarkable group of Germans who fearlessly opposed the Nazis in the very center of their power.

Golden cobblestones remember a time when this small alley was used to avoid having to give a Nazi salute.

When it comes to handsignals (and colonialism) rock always beats scissors.

One of the most influential presidents in U.S. history wanted only this plain, elegant monument as his lasting memorial.

The most accurate timepiece in the world.

A computer bug so primitive it was an actual insect.

There's a 12-foot-tall replica of the Washington Monument hidden under a manhole nearby.

A monument in Washington D.C. marks the spot from which all other roads were supposed to stem.

Appropriation-friendly collection of books, periodicals, and more.

A shining, cold, black organ lies in San Francisco's financial district.

The miraculous hydrant that saved the Mission District in 1906.

A modern mechanical planetary system, part of a 10,000 year clock.

This Parisian fountain is a little bit fantasy and a little bit nightclub.

The curious underground history of keeping Paris clean.

Go surfing on this urban wave, "hacked" by local surfers.

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

A restaurant and observation deck built in a unique broadcasting antenna.

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

A Museum Dedicated to the Heroes That Fight Fire.

The likeness of the Baltimore music icon was unveiled in time for the anniversary of his Senate hearings on music censorship.

This peculiar border irregularity is the only way to legally enter Russia without a visa.