Ride the subways of yesteryear.

Under a glass sidewalk lie the remains of some of Manhattan's oldest buildings.

A careful eye can find hundreds of dinosaur tracks running along the Connecticut River.

One woman’s obsession gave birth to this lovely oddity at the Boston Public Library.

Naturally formed white marble arch housed in an abandoned marble quarry from the 1800s.

This headstone-like marker inscribed with three words has been an utter mystery for over a century.

This picturesque abandoned home is rumored to be a spite house.

Home to the Titanic Historical Society's collection.

On top of Gibbet Hill lie the ruins of a lavish turn-of-the-century estate that never quite came to be.

Beautiful steampunk ghosts of early Massachusetts.

Radical Bookstore and Community Space.

The walkable ruins of an 19th century hotel, destroyed in a horse cremation gone wrong.

The 340-year-old house that inspired the classic Nathaniel Hawthorne novel.

A beautiful Victorian-era cemetery, complete with a miniature village.

The site of one of the strangest disasters in history—a wave of deadly molasses traveling at 35 mph.

This industrial area was the dumping ground for massive amounts of trash, some of which washes up as tiny bits of sea glass.

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

This old mill and former police station now present a world-class collection of Orthodox iconography.

Ruins of the elaborate house where the enigmatic costume designer threw glamorous parties for New York's theatrical elite.

Each of these gorgeous, intricately decorated rooms is painstakingly crafted to the scale of 1 inch: 1 foot.

A memorial to the unknown and unheralded men and women of the Cold War military and intelligence services.

New York City's smallest piece of private property.

This faux-seedy Japanese arcade is made up to look like a maze of alleys straight out of a cyberpunk dystopia.

There are owls with glowing eyes in Herald Square.