Try not to get slimed in Tribeca.

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

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

A terrific purveyor of natural history objects and curios.

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

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

A tiny museum housed in a New York freight elevator specializes in the "overlooked, dismissed, or ignored."

The oldest building in the District of Columbia was preserved because of a mistaken connection to George Washington.

Go take a picture with the inventor of the daguerreotype photographic process.

The remains of Martha, the last known passenger pigeon, serve as a tool to educate about conservation.

A Civil War fort in the middle of Washington, D.C. has been swallowed by a forest.

Franciscan monks created a facsimile of the Holy Land for North Americans who couldn’t afford the trip overseas.

Fittingly, America's museum of architecture is itself a magnificently designed old building.

This grand gothic brewery has been pumping out suds for over a hundred years.

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

Home to items never before seen by the public.

The United States Capitol's former columns still stand.

Countless grotesque faces stare out from this eerie Prague art wall.

A Jenga-style cylindrical tower of books that appears to go on forever.

A medieval bridge stretches over a sulfur-rich river that leads to year-round natural hot springs.

A vast, otherworldly collection of Buddhist stupas.

These crumbling towers are some of the last remnants of a centuries-old Vietnamese culture.

This Vietnamese hell cave lets visitors take a walk through a devilish underworld full of demons.

World's largest cave was only discovered in 1991, and now offers tours to the public.