This mysterious marker puzzles pedestrians and infuriates geographers.

Holding the most bodies of any cemetery in the United States.

An odd, ancient window that may have once been part of a brutal prison is embedded in the side of New York's Police Plaza.

This Upper East Side apartment co-op was designed as a tuberculosis sanitarium.

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

Fake subway tiles were installed to cover a design that resembled the Confederate flag—it's unclear if the resemblance was intentional.

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

During the 19th century, you could pay for violence off a prix fixe menu on this Manhattan street.

Built just after the American Revolution, the oldest row house in New York City still stands in Chinatown.

A historic 1890s architectural masterpiece with an iconic clock tower that, once open to the public, now faces an uncertain future.

Deep under Manhattan is the largest construction project in city history. So far, the project has taken the lives of 23 workers, or "a man a mile."

An accidentally hidden library containing the ephemeral history of New York.

This slender three-story building has also had several famous residents.

This translucent sculpture represents a quintessential component of New York City's skyline.

A small peaceful park and waterfall tucked amid the urban grind of Midtown Manhattan.

An idyllic mineral hot springs facility with a more-than checkered past.

Who needs fancy modern water slides when this giant North Carolina rock works just as well?

A 315-foot spire jutting out from the Blue Ridge Mountains makes for breathtaking views.

Inside this old train depot resides a multi-line model train covering western North Carolina.

A nourishing complex of found object art, paintings, and sculptures that celebrate key figures in Black history.

The U.S. Supreme Court's secret Cold War relocation facility in the mountains of North Carolina.

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

This family cemetery is a reminder of a smallpox outbreak in late-19th-century Texas.

This seaworthy collection was sparked by one man's passion for sailing.