Rummage through this sunken ship, but leave your scuba gear at home.

An unassuming secret door once led to a legendary watering hole.

Slyly buy a shake in the Parker Meridien lobby.

The famous facade of Grand Central Terminal hides a regulation tennis court, and it's not the first one.

Long the exclusive domain of birds and vagabonds, this little-known Central Park peninsula is open to the public once more.

A miniature rainforest is growing inside of a Midtown Manhattan office building.

A once crucial portion of the Long Island railroad still lays abandoned, waiting to be turned into an urban park.

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

This ruined fort hidden at the top of Central Park can't seem to keep from losing its historical plaques.

The "Seinfeld" diner.

This was one of the first (and last) university-built and operated nuclear reactors.

Visit the monolithic tomb of America's most famous general.

Home to the infamous "Typhoid Mary" and the worst loss of life in New York's history prior to September 11, 2001.

A crumbling staircase in upper Manhattan is all that remains of one of the most important sites in sports history.

The loneliest island in New York.

A former connection to City Island, it has been abandoned since the 1930s.

This once-grand marvel of engineering is now 41 miles of scenic hiking trail.

An abandoned horticulture institute gloomily presides over rows of derelict and vine-wrought greenhouses.

A factory director designed what was the world's longest suspension footbridge in 1923 so his employees could get to work safely.

A dead saint, a deadly poison, and a mysterious holy ooze.

A cave in southern Italy adorned with thousand-year-old Biblical frescoes existed in obscurity until fairly recently.

One of the highest emergency huts in the world has been waiting almost a century to give imperiled climbers a place to lie down.

A petite white lighthouse perched on the ancient core of Stromboli Volcano.

The oldest volcanology research center in the world.