At Washington's Dulles Airport is a satellite museum (no pun intended) with three quarters of a million square feet of aircraft history.

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

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.

Collecting 700 years of mechanical death-dealing, the NRA's sprawling gun museum is a revealing testament to the American obsession with armament.

The semi-reclaimed ruins of this canal were once part of an ambitious plan to reroute the mighty potomac.

The Dover International Speedway is home to a towering, concrete-skinned, racecar-hungry behemoth.

World War II-era bunkers are hidden under the beaches of this picturesque park, which is still scattered with wartime watchtowers.

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

This lush forest valley was once mined for lumber to the extent that it was once nicknamed "The Pennsylvania Desert."

This palatial botanical garden is home to one of the largest pipe organs ever installed in a private residence, and a piece of Wood's cycad.

Once the "Eighth Wonder of the World," this iron railroad bridge was decimated by a tornado.

This charming colonial alleyway is one of the oldest continuously used residential streets in the U.S.

A toxic ghost town sitting atop a massive coal fire.

Hidden for 165 years inside a building designed by Thomas Jefferson are the remains of what may be America's first educational chemistry lab.

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

An organ located deep within a cave, whose "pipes" are the geological features of the cave itself.

The world's largest mountain carving could fit all of Mount Rushmore inside it many times over.

An obscure waterfall that looks like something out of a fantasy novel.

A wall of chewing gum moonlights as collective art.

The largest hot spring in the United States is, as the name suggests, a stunning show of natural color.

One of nature's most well-scheduled phenomenons resides in Wyoming's Yellowstone National Park.

This rustic old building is said to be the most photographed barn in America.

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.

The preamble to the U.S. Constitution written entirely from vanity license plates hangs in the Smithsonian museum.