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

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.

The monument's pointy aluminum tip has been melted down by repeated lightning strikes.

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

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

A gift from Japan, 17th-century lantern stands among the cherry trees at D.C.'s Tidal Basin.

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

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

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

Decades before the scandal, this staircase on the river was a literal "water gate."

The word "Watergate" will forever be associated with the infamous scandal in 1972, but this fountain is famous in its own right.

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

A portal into the bricked up canal that runs through the heart 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.

This church built atop a gas station promises to "equip you for the next stage in your life’s journey."

At 207 feet, one of the world's longest continuous escalators.

This unique historical monument features large concrete spheres designed to resemble fallen stars.

An oft-overlooked, magically musical monolith that stands majestically between Arlington Cemetery and the Iwo Jima Memorial.

Hear, smell, see, taste, and touch history at this immersive Civil War hospital.

This train station inspired the name of a 1970's rock band and provided the backdrop for their album cover.

This Federal-style plantation house was once visited by Abraham Lincoln to meet with generals during the Civil War.

The tomb was guarded by soldiers from both sides of the war, and some left their initials carved in the brick.