A curious carving hides on a marble column in the Mosque-Cathedral of Córdoba.

Tour the dark and beloved poet's former cobwebbed basement, which may have inspired "The Black Cat."

A tiny monument to the unsuccessful attempt by Thomas Jefferson to place the prime meridian in Washington.

The only National Monument ever to go missing for nearly 50 years then resurface in a dump.

An overlooked memorial honoring the local Washington residents who died in World War I.

Those with a sharp eye can find the hidden image of a German Shepherd on the memorial's Mural Wall.

The beloved statue at the National Academy of Sciences is oh so inviting to sit on.

This seemingly out-of-place gas station by the Watergate hotel was once described as the most expensive gas station in the world.

The oldest building in the District of Columbia was preserved because of a mistaken connection to George Washington.

The national park was once a plantation estate.

Soldiers were buried next to Lee's house in the center of Arlington Cemetery to dissuade the general from reclaiming his property after the war.

The graveyard holding the remains of George Washington's slaves was forgotten for nearly 200 years.

The story behind the mysterious symbol painted in front of the historic university's famous Rotunda.

Built by the patriotic residents of Boonsboro in a single day.

The trials and tribulations of marking Poe's grave.

A dramatic, 360-degree recreation of Pickett's Charge in the Civil War.

This small section of the Sleepy Hollow Cemetery is rotten with famous authors' graves.

The nation's second-ever First Lady urged the founding fathers to "remember the ladies."

The homestead of American patriot John Adams.

Site of an oft forgotten and revolutionary battle.

One of America's most historic homes also holds a startling literary legacy.

This impressive Boston holy house is the American mecca for Christian scientists.

An enormous, inside-out glass globe built in 1935.

American revolutionaries and British soldiers alike are buried here in the fourth-ever cemetery in Boston.