This fortified sand barrier dividing a contested territory is the longest minefield in the world.

Peace Park and the Atomic Bomb Dome.

A plaque marks the site directly below the mid-air detonation of the atomic bomb over Hiroshima.

The last holdout of a pre-Civil War rebel who took the matter of slavery into his own hands.

These disused steel furnaces are now haunting ruins that may one day be a national park.

The site of the first couple's first kiss is commemorated by the most adorable presidential monument ever.

A celebrity from the late Cretaceous period.

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

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

The sculptor was instructed to add “stallion attributes” to the general's bronze mare.

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

A 1,100-ton train fell through the floor in 1953. Workers got it patched up in just 72 hours.

An overlooked memorial honoring the local Washington residents who died in World War I.

There’s a hidden military meme engraved on the World War II Memorial.

A monument celebrating the idea of reaching inaccessible places.

"We Seceded Where Others Failed."

A stone slab in Madrid marks the point from which the distances of Spain's national roads are measured.

The span is crooked and made from two older recycled bridges.

It was once the base for a series of domestic terror attacks.

This beautiful stone arch bridge wasn't even expected to stand for one day, but people have been crossing it for centuries.

FDR's Art Deco hospital tower was hopelessly inefficient.

The 5.5-mile ring of steel posts around the Capitol Building is one of the largest (and most uniform) of its kind in the world.

The marker offers a rare chance to be in four U.S. states at once, though there's some controversy over its geographic accuracy.

This abstract sculpture is rumored to cast a hammer-and-sickle shadow once a year.