The little-known, 300-year history of the area includes former lives as a bustling tobacco port, parking lot, and industrial dump.

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

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

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

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

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

This mysterious structure by the Washington Monument is a flood barrier designed to protect the White House against rising waters.

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

A bas relief commemorates the "Nuns of the Battlefield" who cared for soldiers on both sides of the conflict.

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

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

"Congress may voluntarily remain in session throughout the summer, in order that our Congressmen may be protected from the intolerable discomforts and dangers of the ordinary outdoor weather!”

Once the supplier for noteworthy projects like the National Cathedral, this old brickworks now lies abandoned.

A historic ruin just 20 feet away from a busy highway onramp.

A monument in Washington D.C. marks the spot from which all other roads were supposed to stem.

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

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

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

The national park was once a plantation estate.

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

The remains of Martha, the last known passenger pigeon, serve as a tool to educate about conservation.

A traveling postal dog covered 48 states and more than 140,000 miles, and he lives on as taxidermy, patched up with a rabbit's foot and a pig's ear.

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

One of the dwarven trees dates back to 1625 and survived the Hiroshima bombing.