A Pythagorean funhouse that tries, successfully, to prove that math is the coolest thing ever.

A treasure trove of artifacts, books, and artwork from the "golden age" of exploration.

Tucked in the back of this amazing antique store is an important piece of medical history.

A crumbling hospital from the 1850s on Roosevelt Island.

A terrific purveyor of natural history objects and curios.

La Monte Young and Marian Zazeela's "Dream House" will immerse you in an ever changing world of sound and light.

A beautiful and abandoned New York subway station from 1904, complete with chandelier.

People escaping slavery may have hidden inside a corpse vault.

Decades before the scandal, this staircase on the river was a literal "water gate."

D.C.'s first central library was born out of a chance encounter with the philanthropist whose name it bears.

The remains of Martha, the last known passenger pigeon, serve as a tool to educate about conservation.

A painfully obvious spy house sits right across the street from the Russian Embassy.

The house where John Wilkes Booth conspired with his co-conspirators.

The most decorated dog of World War I is preserved in the Smithsonian.

A tiny piece of the Moon is embedded in this stained glass masterpiece.

A school-themed restaurant where gastronomy is the core curriculum.

Ancient human remains unearthed around the iconic monument.

The secluded site of a 1943 plane crash and amazing rescue is only accessible by hiking through the woods.

These century-old beehive-shaped kilns were built to produce charcoal for nearby mines.

Rare and gorgeous birds abound in this protected wildlife sanctuary.

See just what life was like in a 19th-century prospecting town.

A petroglyph map of the upper Snake River carved by prehistoric hunter-gatherers.

Despite his legacy of work in Spain, Cuba, and Florida, the larger-than-life writer's grave is a simple affair tucked in an Idaho cemetery.

These black pillars of volcanic basalt seem to call mountain climbers with an unbreakable siren song.