Try not to get slimed in Tribeca.

La Monte Young and Marian Zazeela's "Dream House" will immerse you in an ever changing world of sound and light.

A huge musical instrument played by the ocean.

Take an otherworldly journey in a school dedicated to out-of-body experiences.

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

19th century museum with an eclectic mix of curiosities, from Egyptian artifacts to items on archery history to the skull of the world's oldest horse.

The oldest inn in England served brew to the crusaders.

A thousand year old oak tree survives in Liverpool.

A gender-bending antihero's grave, where lies the inspiration for both book and film.

A beautiful maze marks where three countries meet.

Incredible labyrinth of man made caves.

Museum in a swimming pool where the water still flows.

Hiding the longest subterranean river known in the world.

6000-year-old site covered in more than 50 megaliths.

Seat of the Duke and Duchess of Devonshire for centuries.

A preserved 18th century steel factory.

Macabre astrological automaton clock dating to the late 1400s.

An original apothecary from 1792.

A secretive collection featuring objects that were designed specifically for U.S. intelligence operations.

Daily lunch spot for many of Washington, D.C.'s cab drivers.

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

Ancient man-made caves underneath small town Belgium.

A visionary precursor to the Internet made of index cards.

A pilgrimage site where people ask Saint Dymphna to watch over those who are not of sound mind.