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

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

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

D.C. once had its own tiny rival to the New York Stock Exchange.

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

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

A memorial to a shareholder activist feared by CEOs around the United States.

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

The U.S. Navy’s preposterously detailed mini battleship took 77,000 hours to complete.

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

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

This grisly headstone doesn’t seem to be resting in peace.

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

One critic described it as "middle Mussolini, early Ramses, and late Neiman-Marcus." Another called it an architectural "natural disaster."

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

These abandoned waterworks are crumbling into the Potomac River.

A 1,100-ton train fell through the floor in 1953. Workers got it patched up in just 72 hours.

An obscure federal monument honors the French diplomat who served as Ambassador to the U.S. during WWI.

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

‘Bush the old fire dog died of poison July 5th, 1869. RIP.’

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

More than 500 unique and specially designed cases collected by D.C.'s "Harmonica Case Man."

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

A derelict bit of infrastructure from the canal that once ran through D.C. is landlocked in the heart of the city.