The "Key of Keys" for Washington, D.C. and the apocryphal landing place for the military campaign that started George Washington's career is now at the bottom of a well.

The Lincoln Memorial has inspired many, even though a word on the inscription appears to be spelled incorrectly.

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

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.

One of the last mosaic tile facades found in the city.

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.

This statue of one of baseball’s greatest pitchers looks like something out of a sci-fi horror movie.

The innocent intentions of this monument are somewhat lost in the sculpture's muscled imagery.

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

"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!”

One of the most influential presidents in U.S. history wanted only this plain, elegant monument as his lasting memorial.

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

Before Metro, Washington had a robust streetcar network—and you see the remains of this infrastructure if you know where to look.

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

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.

Daredevil repair workers can worm their way out the access hatch, loop ropes over the apex and rappel down the monument.

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

The National Park Service’s best-kept secret with views that rival any in D.C.

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

Art deco landmark on the outskirts of Washington, D.C.

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

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