Cryptic messages embedded in the New York City sidewalk.

This mosaic dedicated to John Lennon was tended for years by a Beatles super-fan.

First a horse rendering plant, then a 19th century landfill, this beach is full of glass from thousands upon thousands of broken bottles.

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

Elevated freight railway turned wildly successful urban park.

This hospital fell into ruins after failing to act as the advocate for the mentally ill it was designed to be.

Infamous marsh filled with toxic waste, World War II-era London rubble, and dead mobsters galore.

How this Pine Barrens hill got its name is uncertain, but on a good day the view from the fire tower is crystal clear.

These unassuming lighthouses have seen the first reading of the Pledge of Allegiance, the first wireless transmission, and more than one mystery.

Local lore claims this park is named after a young woman who jumped off a cliff.

Rusting away on the edge of New Jersey are the remains of a Cold War missile launch site.

A completely round house designed for the Atomic Age.

Once the world's largest reinforced concrete structure, this abandoned bridge now beckons urban explorers.

The remains of an old sawmill, gristmill and the surrounding industry dating back to the 18th century.

The rusting remains are visible sticking out of the waters of the Delaware Bay.

A unusual sanctuary for abused and exotic animals in South Jersey.

Now abandoned, the first public health hospital in the U.S. saw more than one million immigrants from around the world.

World War II bunker still standing on the New Jersey beach.

Destructive children, start your engines.

Step inside Lucy, the world's largest "elephant."

One of the world's largest model railroads is a mind-boggling achievement.

In the woods of New Jersey lie the ruins of a munitions village abandoned after World War I and the remnants of a 1920s wooden racetrack.

This historic iron-working village is now a ghost town so immaculate that it looks as though it was recently built.

The site of one of history's most indelible and horrific tragedies.