One of the oldest of its kind.

Erected in 1697 this Philadelphia bridge is the oldest surviving roadway bridge and perhaps the oldest stone bridge in the United States.

This elaborate towering structure was once famed for its revolutionary height.

Ant sculptures march up the side of what used to be an iconic spot in punk rock lore.

A clone-tree in Washington Square Park sprung from seeds that went to the Moon and back.

Where America's first doomsday cult awaited the end of the world.

World's first "penitentiary," meant to be humane, drove men insane.

The abandoned grounds and derelict greenhouses of this once-magnificent Edwardian estate are now a nature preserve open for exploration.

This forgotten graveyard in rural New York State once served a pioneering hospital.

An abandoned Gold Coast-era mansion once intended for the exiled ruler of Albania, who never arrived.

A millionaire's abandoned swimming pool from the gilded age of one of America's most distinguished families.

This graceful little figure is a one-of-a-kind version of the cherished character.

Beneath the mossy overgrowth covering this once-sprawling campus lies decades of history and the secrets that come with it.

A long abandoned hospital building on the outskirts of NYC.

A massive forgotten storehouse from 1913 on the Brooklyn Waterfront has a spectacular view of Brooklyn.

A remnant from the golden age of aviation still in use today, Pan Am's Clipper service took off from this Art Deco gem.

A mysterious statue of a leather jacket-clad rebel leans coolly on an odd yellow clock.

Guerilla gardeners reclaimed this abandoned railroad land literally putting down roots.

Two New York rooftops are home to the largest rooftop soil farms in the world.

A small structure built from used railroad ties honors the short term of America's 20th president.

This crumbling little graveyard was saved from the undergrowth by concerned veterans.

The final resting place of a famous 19th-century murder victim whose identity is still a mystery.

New Jersey's last historic covered bridge was rebuilt from pieces of the original 19th-century structure.

Edison's cast-in-place concrete houses were a failure, but way ahead of their time.