A collision of human error and natural geothermal pressure created this rainbow-colored geologic wonder.

This beautiful building in the heart of Manhattan's Financial District was empty for decades.

An emerald-green grotto just a short trip from Austin.

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

On the Oregon coast there is a natural hole that seems to be draining the sea.

Most-visited and most-photographed slot canyon in the American Southwest.

A crumbling hospital from the 1850s on Roosevelt Island.

This iconic L.A. bookshop is housed in an abandoned bank—both symbolic and chic.

Bring your own cardboard to the slippery slopes of concrete hidden in a neighborhood park.

A psychedelic labyrinth on the San Francisco bay.

America's most famous museum of medical oddities is home to the remains of Albert Einstein's brain.

Rippling sand dunes frozen in the Arizona rock.

A terrific purveyor of natural history objects and curios.

A huge musical instrument played by the ocean.

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

There's nothing shrimpy about the world's largest artificial prawn.

World's oldest operating science fiction and fantasy club, once home to Ray Bradbury and L. Ron Hubbard.

The oldest bibliophilia club in America, with exhibitions on historic books and graphic arts.

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

The oldest family-run luncheonette in New York, last renovated in 1948, still serves food and drinks the old-fashioned way.

This lavish room at NYC's French Embassy is a rare relic from the end of the Gilded Age.

This whimsical group of statues is a favorite of children who love to climb all over Lewis Carroll's beloved characters.

The name of this tiny pocket park tucked between two buildings on Manhattan's Upper West Side is Latin for its location: "seventy-one."

A memorial to the first person killed by a motor vehicle in the Western Hemisphere.