A 19th-century subterranean reservoir repurposed as a contemporary art cave.

These tourist trap caverns are said to be the former home of a legendary Pennsylvania Hermit.

This valley of hot springs and boiling mud pots is home to the record-holding "Geysir," which originated the English word.

Rent out a glass igloo to watch the Northern Lights like you live in the future.

A metal tree emits eerie, melodic notes on top of Lancashire's Crown Point.

The longest navigable underground river in the United States is home to countless blind and albino animals.

This unauthorized stone mermaid was secretly carved out of public stone before being permanently preserved.

This lake in the Cascades lives up to its name, disappearing down a hole every spring.

Outsider Art Community.

A wondrous old library overlooking the nation's capital.

A Swedenborgian glass church surrounded by redwoods sits perched atop a massive landslide area.

An alleyway plaque is all that remains of the independent Texas' envoy that forgot to pay their rent for over a century.

This Irish show cave is said to have been the site of a Viking massacre that claimed 1,000 lives.

This futuristically sylvan church is a glass-enclosed marvel of modern architecture.

Tiki luxury on Nob Hill.

Perfectly preserved ancient monastery in an impossibly dramatic location on a rocky island in the Atlantic.

A prohibition-style speakeasy takes up residence in the last Victorian residence in Hollywood.

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

Mysterious rocks that ring musically when struck.

One of the oldest medical collections in Europe focusing on rare surgical instruments.

This secluded aqua waterfall in the Grand Canyon is the perfect swimming hole, and the Havasupai tribe's fiercely protected natural wonder.

A snapshot of the city's fascinating voodoo culture.

Tucked in the back of this amazing antique store is an important piece of medical history.

A psychedelic labyrinth on the San Francisco bay.