Under a glass sidewalk lie the remains of some of Manhattan's oldest buildings.

The world’s oldest and biggest bookstore stocking only mystery, crime fiction, espionage, and thrillers.

The home of the first American-born saint is one of the only curved buildings in New York.

This block in downtown Brooklyn was a hotbed of antislavery activism along the Underground Railroad.

Imagine having a street run right through your home, or better yet, a historic bridge three stories high.

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

If it hadn't been caught in time, a flaw in the design of this Manhattan skyscraper could have led to its collapse.

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

Since it formed millions of years ago, this cave system has been a sacred burial ground, a Prohibition-era speakeasy, and the center of an amusement park.

This fountain was commissioned by a mother grieving over her son's passing.

Abstract marble carving for an 8.5-pound rock.

A propulsion engine testbed that paved the way for the Space Shuttle launch sits without recognition at this rocket center.

It may look like no more than a full-scale model, but every part of this full Space Shuttle stack had a working role in aviation history.

The terrified face of Henry Wells is etched on this garret window.

Colloquially known as "the lynching memorial," this is the United States' first memorial to the victims of racial terror at home.

A 56-foot tall statue of the god of fire looks out over Birmingham, Alabama.

This 1,500-acre development hopes to be the Central Park of the South.

The country music legend's grave is surrounded by Astroturf because fans kept plucking out the grass.

Once one of the largest producers of pig iron in the world.

A collection of huge Pre-Colombian structures in Alabama.

Designed by Maya Lin, the memorial honors 41 individuals who died fighting for equal rights between 1954 and 1968.

Bananas are often left for the first monkey America ever recovered alive after being launched into space.

A miniature city built by a single hunchbacked monk.

The oldest operational cathedral in the U.S. has one shell of a way of projecting speakers' voices.