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.

Walk over a 150 year old manhole.

A strangely angled West Village home is the only monument to an explosion that took the lives of three American revolutionaries.

New York's unstoppable progress turned this cemetery into the smallest burial ground in the city.

The greatest real estate coup of all time.

Manhattan's deadly West Side railroad, which killed hundreds of New Yorkers, is remembered by this simple plaque.

The 28-foot granite map plots the locations of 40 theaters in New York City.

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

A Manhattan courthouse hides a small but scathing memorial to Holocaust injustice.

This monument to a veteran of the Mexican-American War is one of only two in Manhattan that serve as an actual mausoleum.