The one-time epicenter of American songwriting is now a little remembered Manhattan commercial block.

Cryptic messages embedded in the New York City sidewalk.

The former hotel where Tesla invented the radio.

Commemorating the spot where the famous scientist fed his pigeons.

There must be a pun in this haystack somewhere...

One of the oldest anatomical theaters in the U.S. still in use was once the site of an infamous cadaver riot.

The oldest living tree in Manhattan comes shrouded in sinister legend.

Red frames showcase remnants of one of New York's original subway stations.

FDR hoped to find a cure for polio in this Georgia town's warm springs.

An eerie smiling woman looms above the granite tombstones.

This unmarked and unloved Manhattan subway grate created one of the most iconic images in American cinema.

This castle-like building in Manhattan helped destigmatize cancer in the 19th century.

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

Possible relics of the ancient Roman city are hidden in this restaurant's façade.

New York City's smallest piece of private property.

A popular European tradition makes its way to the states on one of America's most famous bridges.

Touching mementoes from those who didn't make it back from World War I still hang in one of New York's oldest bars.

These historic buildings once housed the headquarters of one of the most infamous gangs of New York.

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

Elevated freight railway turned wildly successful urban park.

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

The artist and New York City icon lived, worked and died in this converted carriage house owned by another iconic artist, Andy Warhol.

The competition: breathe deeply as long as you can.

A terrific purveyor of natural history objects and curios.