The second-largest cave chamber in the world was discovered in 1898 by a 16-year-old and a friend known as "Pothead."

More gold than anywhere else, ever.

A self-built castle made by a mysterious man.

Franciscan monks created a facsimile of the Holy Land for North Americans who couldn’t afford the trip overseas.

Take a drunken tour inside the world's largest known geode.

New York City's smallest piece of private property.

Hidden in Central Park's Ramble is a troublesome cave buried just beneath the surface.

A museum befitting the city responsible for supplying the majority of the world's LSD.

Odd outsider art installations surround a Gold Rush-era ghost town.

With over 100 jam-packed rooms to explore plus elaborate tea services and events, the Mansion on O Street is a hidden treasure.

A hands-on traveling collection of the innovative devices of yesteryear.

Home to items never before seen by the public.

Giant busts of 42 U.S. presidents are sitting in a field in Virginia.

The remains of a failed attempt at medieval nerdery are hidden deep in the woods of Virginia.

Four glass boxes hover over 1,000 feet in the air to give visitors an unparalleled view of Chicago.

A hand-built folk art installation covered with messages of God's love.

Where America's first doomsday cult awaited the end of the world.

Eighteen miniature death-scene dioramas.

The rocks in this arid basin leave trails of movement behind them.

This shop for all your super spy needs hides an educational secret.

Shop selling 500 flavors of soda has something for everyone.

The ancient dwellings of the Puebloans, located in the cliffs of majestic mesas.

The United States Capitol's former columns still stand.

A winding path built in secret on the edge of the continent.