Government testing at the asylum briefly explored using marijuana as a "truth serum" on Nazi prisoners of war.

America's first federal monument.

A mammoth pair of Civil War artillery guns abandoned out in the forest.

This fort down the Potomac from Washington, D.C. was once the only defensive fort protecting the capital.

Remains of a historic fountain that was mysteriously lost in the demolition of a D.C. traffic circle.

The Decoy Capital of the World.

The 28,000-year-old specimen is remarkably intact.

This sandwich shop has a century-old elevator behind a sheet of plexiglass.

The fountains of the U.S. Navy Memorial are annually salted with water from the Seven Seas as part of a nautical ritual.

A much-maligned monument to teetotalism.

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

An atomic bomb-proof strongbox protects the U.S. Constitution from terrorists and thieves.

Washington's iconic carousel has a nice piece of Civil Rights history.

This stunning blue and gold room changed cities twice before becoming part of the Smithsonian.

Seemingly unremarkable items like empty sushi trays, chef hats, and freshness stickers are being preserved so future generations can look back on this beloved cultural import.

Perhaps the most scandalous statue of America's first president.

This taxidermy horse was a Civil War hero.

A heroic pigeon that, through a barrage of gunfire, delivered a message that saved over 100 lives in World War I.

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

The U.S. Fish Commission’s effort to mass produce carp.

A tiny monument to the unsuccessful attempt by Thomas Jefferson to place the prime meridian in Washington.

The monument's pointy aluminum tip has been melted down by repeated lightning strikes.

Look closely and you’ll notice that the color changes a third of the way up the tower.

The innocent intentions of this monument are somewhat lost in the sculpture's muscled imagery.