An immense cave that has served as an outlaw's treasure trove, an underground dance hall, a nuclear fallout shelter, and much more.

A small "palace" and museum made of, and devoted entirely, to salt.

This former Texas landfill is flush with 300 million-year-old fossils, all fit for the taking.

It specializes in outsider art and artifacts of secret societies.

A serene temple with stunning stained glass hides in downtown Dallas.

The only diamond mine in the world where you can keep what you find.

The remains of the first public diamond mine in Arkansas.

Home to a seasonal waterfall and swimming hole in the Ouachita Mountains.

Two gushing waterfalls of hot spring water within a block of each other.

Generations of rockhounds got their start at this beloved, historic mine.

More than 350 million years ago, western New York was covered in a vast sea. Today, you can dig up the remains of the plants and animals that lived there.

The only runway directly into the magic kingdom has been closed since 1972, but it still sings to you if you drive fast enough.

This small museum gives visitors a chance to soak up the history of the "sponge capital of the world."

This former factory has been transformed into a technicolor wonderland, where dozens of local artists have collaborated to create a real choose-your-own-adventure experience.

Manatees congregate around a power plant's discharge canal where the water is especially warm.

Florida castle built with aluminum printing plates.

An art collective teaching the more fiery, metal-y art forms.

This small road tunnel is the only place where you can cross beneath the Erie Canal.

A little-visited ghost town state park offers a glimpse into Montana’s "Silver Queen."

A sprawling museum located on the former site of the Orphan Girl Mine.

A working ranch doubles as a sustainable hub for world-renowned classical music and large-scale sculptures.

An apocalyptic seismic event creates a deadly chain reaction that ends with a 6-mile long lake developing within weeks.

The rocks of a certain area of Butte, Montana give off a musical ring when hit.

New fungal and bacterial species call this deadly lake home.