A phenomenal assembly of pueblos in New Mexico is the most complete example of ancient ruins north of the border.

The second-largest cave chamber in the world was discovered in 1898 by a 16-year-old and a friend known as "Pothead."

An immersive environment that is part haunted house, part choose-your-own-adventure, and part jungle gym.

Only known mainland rookery of the threatened Stellar sea lion.

The rogue roots are gradually consuming some of the historic marble grave markers.

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

The tomb was guarded by soldiers from both sides of the war, and some left their initials carved in the brick.

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

This statue of the "father of television" stands prominently in the United States Capitol.

The 5.5-mile ring of steel posts around the Capitol Building is one of the largest (and most uniform) of its kind in the world.

Look closely and you’ll notice that the color changes a third of the way up the tower.

Corn-inthian columns with a uniquely American take on neoclassical architecture.

A muscular Art Deco monument represents the struggle between regulators and unbridled markets.

While most wind tunnels test scale models, the "Cave of Winds" was large enough for actual airplanes.

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

Architecture lovers won’t stop touching the National Gallery's 19.5 degree marble prow.

Washington's iconic carousel has a nice piece of Civil Rights history.

A little marble compass above George Washington's (empty) tomb in the Capitol marks where D.C.'s four quadrants intersect.

Perhaps the most scandalous statue of America's first president.

Rumor has it the uncarved lump behind the three famous suffragists is reserved for the first woman president.

It was once the base for a series of domestic terror attacks.

There’s a hidden military meme engraved on the World War II Memorial.

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

The walls of the iconic dome are hollow and have a secret stairway.