This futuristic German spa allows visitors to float in a pool of salt water while zoning out to underwater techno.

Former drug lord’s manor, now a theme park. Watch out for the hippos.

A dangling church built over a Colombian gorge.

Sweden's first nuclear reactor, R1, can be visited 25 meters underground.

Dr Barnes' $25 billion private collection of art and arboretum.

The iconic Manhattan corner that was once the site of the Beastie Boys' fake clothing store.

The famous facade of Grand Central Terminal hides a regulation tennis court, and it's not the first one.

Ever wanted the laymen's version of your credit card fine print?

The oldest living tree in Manhattan comes shrouded in sinister legend.

A staggering collection of photographs depicting medical, social, and historical change.

Haven for steampunks.

Long the exclusive domain of birds and vagabonds, this little-known Central Park peninsula is open to the public once more.

A quiet and contemplative oasis in the middle of New York's bustle and riot.

Visit the site of a subway powered by nothing more than air--and lots of it.

Named the fifth most beautiful building in America in 1885, this former courthouse boasts the best view in the Village.

Hidden in plain sight on a pair of Manhattan subway tunnels are a pair of public instruments that sing to each other.

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

A tunnel once abandoned now thrives with graffiti art as an off-limits makeshift gallery.

More gold than anywhere else, ever.

A hip bar decorated with walls of golden skulls.

A miniature rainforest is growing inside of a Midtown Manhattan office building.

A beautiful and abandoned New York subway station from 1904, complete with chandelier.

A treasure trove of artifacts, books, and artwork from the "golden age" of exploration.

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