The remnants of a wooden-hulled fleet built and abandoned in WWI, now home to a thriving ecosystem.

An eerie, decaying ghost town destined to fade into the forest.

The haunting "Hell House Altar" is one of the few remnants of an abandoned college that has been a magnet for local legends.

Eighteen miniature death-scene dioramas.

This groundbreaking 16th-century map is known as "America's birth certificate."

On the Fourth of July this area will transform into a Pompeii-like storm of falling embers and ash.

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

The only tennis court that falls under the jurisdiction of the central bank.

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 tunnel under the Capitol Building where Congress takes out its trash.

Disks are rolled out onto the south lawn to absorb the impact of Marine One's wheels like giant coffee coasters.

The grand marble structure next to the White House is Andrew Carnegie's temple to Pan-American diplomacy.

After his presidency, George Washington planned to live only a few blocks from the Capitol building.

An ear-piercing buzzer calls lawmakers to a vote with a series of long and short rings to form coded messages.

Every drop of D.C. tap water flows through this old waterworks.

This taxidermy horse was a Civil War hero.

A line of blue paint marks the route of the inaugural parade.

The elevator that makes it possible to fly American flags in bulk over the U.S. Capitol

An 18-mile-long tunnel for sewage waste will soon wind within the bowels of Washington, D.C.

A promising candidate for the lost rock laid by George Washington was unearthed, but the hunt is still on.

Part of a WWII submarine is lurking outside the Washington Navy Yard parking lot.

A portal into the bricked up canal that runs through the heart of Washington D.C.

The 28,000-year-old specimen is remarkably intact.

The school tested mustard gas for the U.S. Army during World War I.