Wild lights and sound effects turn a walk through some caves into an eye-popping 1960s tourist attraction.

One of New York's best collections of pinball is hidden in a secret bar in the back of this laundromat.

The largest hot spring in the United States is, as the name suggests, a stunning show of natural color.

One part antique store, one part curiosities hodge-podge.

The largest self-built castle in the U.S., six decades in the making.

A hidden network of subterranean passageways lies tangled beneath Indianapolis' bustling City Market.

A modernist landscape of water and sci-fi concrete.

This incredible collection of vintage pinball machines can be played at 25 cents a pop.

Frank Lloyd Wright's most iconic home dangles over a Pennsylvania waterfall.

Sniff the Titan Arum's rotting flesh.

Towering basalt columns, a creation of fire and ice.

A heavenly experience, right here on Terra Firma.

This geothermal hot spring hides beneath a slowly growing mineral dome.

A strange house built only at night, with rumored mystic inspiration.

These delicate buggers are some of the rarest fossils that have bubbled up from the Tar Pits.

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

A speakeasy takes on Chicago's drinking culture.

A self-built castle made by a mysterious man.

This naturally-sourced hot spring is now home to a clothing-optional resort.

Where beautiful signs live on forever.

This little museum is built on a theater that was once a wildly elaborate speakeasy.

Seemingly grown on some other world, these New Mexico rock formations look like a disused science fiction set.

A beautiful geyser under environmental threat.

This upscale streetwear store is hidden behind a fake Snapple machine in the back of a deli.