Try not to get slimed in Tribeca.

An uber-secure, windowless tower of doom in the center of Manhattan is an NSA spyscraper.

Waterway populated with abandoned projects, including a submarine.

This small, hidden cove is home to abandoned boats.

One Brooklyn man's collection of life-size fiberglass statues has taken over his entire yard.

The highest point on the island known for buildings that touch the sky.

This hidden oasis features a stunning view of the Hudson River and the Palisades from a castle-like museum.

Mysterious 500-year-old tapestries depict a unicorn hunt.

No monkeying around, this fountain was really named after the classic sci-fi film.

The remnants of two World's Fairs are here, complete with a 12-story globe, a mini-Manhattan, and a UFO-shaped pavilion.

The oldest surviving bridge in New York City, which reopened to pedestrians in 2015.

Millions of numbers carved in glass represent the tattoos forced upon victims.

Historic Hull Street was actually the first street with a proper name in the Boston area.

A mysterious stone embedded at the base of a historic Boston building.

From bench to vandalism to art, this silly prank seat was funny enough to become permanent.

Ice cream stand, snack bar, and time capsule of milk conveyance.

Narrowest house in Boston.

This impressive Boston holy house is the American mecca for Christian scientists.

This area was once known for being a lawless haven for rough-and-tumble sailors, earning the maritime-themed nickname "the black sea."

This massive tea kettle was once a promotional stunt for the Oriental Teashop.

Mrs. Mallard and her brood are a beloved fixture in Boston Public Garden.

The Boston square dedicated to the dark poet who was born nearby.

Two thousand artifacts from around the world collected by one woman who loved to travel.

An enormous, inside-out glass globe built in 1935.