Cave on extinct volcano, once home to famous mathematician Pythagoras.

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

An extraordinary mechanical calculator designed by the mathematician and philosopher Gottfried Leibniz.

This hands-on math museum believes in turning concepts into constructs.

This massive steel pyramid can be entered by a set of jagged steps that let visitors stand in its heart.

This peculiar museum offers hands-on interaction with seemingly intangible principles of mathematics.

The lab where the scientist made his groundbreaking discoveries is preserved on the basement floor of the Faraday Museum.

These beautiful objects represent beautiful ideas.

Four-story slides send people whizzing through the math department at this Munich university.

A plaque marks the house in Stockholm where the French philosopher René Descartes lived up until his death.

The beautiful non-repeating pattern honors the Oxford professor who discovered it.

The only microgravity tower in Europe can produce nine seconds of weightlessness.

This improbable contraption was passed down through five generations of industrious Tennesseans.

Nuclear reactor created the plutonium used on Nagasaki.

The iconic D.C. restaurant where the Cuban Missile Crisis was negotiated, now a Walgreens.

America's Most Wanted's set resides in this tribute to the history of crime and punishment.

Bar full of oddities, specimens, artifacts and homages to the great dime museums of the past.

Now a living classroom, this house was once the home of Reverend James Clinton Dent, a formerly enslaved man and a pastor.

This apartment building designed by a notable Washington D.C. architect housed the Qing Dynasty's Legation.

An echo chamber with a waterfall wrapped around its base at the Embassy of Canada in Washington, D.C.

The world's oldest soul food restaurant is also one of its best.

An amazing example of early-20th-century architecture, this church features marble transported from Utah.

This fertility idol of questionable authenticity inspired an iconic Indiana Jones artifact.

The oldest house in Washington, D.C. wasn't originally constructed in the nation's capital.