Grotto replete with mystical designs laid out in glued shell mosaics.

The only intersection in America where the buildings on all four corners were built pre-Revolutionary War.

The second oldest Jewish graveyard in the U.S. is tiny, with connections to George Washington and Henry Wadsworth Longfellow.

Mysterious stone tower featured in many alternative histories of the New World.

An easily overlooked stretch of ornate window fronts and gaslight lamps that could be right from the pages of Dickens.

London's creepiest cemetery was once the site of dueling magicians and mobs of stake-carrying vampire hunters.

This churchyard arbor is surrounded by hundreds of gravestones placed there by author Thomas Hardy.

This ornate Victorian marketplace was the setting for Diagon Alley and the Leaky Cauldron in the Harry Potter films.

Read between the lines of the subway map to find the hidden abandoned Civil War fort.

This cemetery has graves dating back to the 17th century, including the city's oldest carved tombstone and an ominous cryptogram.

One of only two commuter aerial tramways in the United States.

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

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

A crumbling hospital from the 1850s on Roosevelt Island.

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

One of the earliest bowling lanes in the U.S. doubled as a sewing school during a time when women had little job opportunity.

This tiny church near Sleepy Hollow contains Henri Matisse's last work, a rose window, and nine windows by Marc Chagall.

Oldest existing church in New York and the inspiration for Washington Irving's "The Legend of Sleepy Hollow."

What was once a trend-setting, phrase-coining icon of architectural splendor is now a rotting, forgotten hulk.

This once-private estate is now a dreamy, meditative garden that's open to the public.

The abandoned husk of a mental institution that failed to save a Jazz Age icon still sits nearly unchanged.

A ruined mansion hidden in the woods of the Hudson Valley, home of a tragically doomed romance.

This mouldering abandoned mental hospital was once a center for progressive healing.

This old cement mine has been used as everything from a mushroom farm to a recording studio.