A cave 150 feet beneath Kansas City is the perfect climate for growing 10,000 delicate orchids.

Like Stonehenge, but with boats and oodles more charm.

The world's largest collection of fine-scale miniatures and one the nation's largest collections of antique toys.

This historic cliffside mansion uses a natural cave for air conditioning.

The house where the famed outlaw was shot by a dirty coward is now a museum to the criminal's legacy.

A mysterious light of unknown origin on the backroads of Missouri.

A geological oddity formed by two rivers carving out a mass of limestone on both sides.

A museum celebrating the Victorian obsession with hair art.

This abandoned prison castle has become an imposing gallery of graffiti art.

Curious cave that stays a cool 56 degrees all year long.

A historic estate packed with George Washington's heirlooms, and its own nuclear bunker.

The discovery site of the "Capitalsaurus," the official dinosaur of Washington, D.C.

This robust fence in front of a historic Georgetown home is likely made from hundreds of recycled Revolutionary War firearms.

A historic ruin just 20 feet away from a busy highway onramp.

Largest Roman Catholic church in North America.

An obscure public service from the U.S. government that redeems burnt, moldy, and soiled old greenbacks.

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

An overlooked oasis of quiet on the grounds of Washington's monumental basilica.

There's a crumbling old mansion inside the Smithsonian National Zoo.

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

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

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

A small triangle of DC grass is the final resting place of one of Sonny and Cher's songs.

Long-abandoned trolley tunnels just a mile away from the White House are turning into an art space.