In all of the 29 years it was in operation, no prisoners ever escaped successfully... or so they claim.

A huge musical instrument played by the ocean.

The bank that helped fund the Mexican-American War and the purchase of Alaska met its downfall after helping Augusto Pinochet launder money.

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

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

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

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.

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

The first memorial dedicated solely to the Black troops who fought for the Union.

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

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

The only National Monument ever to go missing for nearly 50 years then resurface in a dump.

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

When it comes to handsignals (and colonialism) rock always beats scissors.

This forgotten boat elevator was an engineering marvel in its heyday.

A building shaped like the Army Corps of Engineers logo, because why not?

This poor little statue is the most vandalized memorial in Washington.

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

The most accurate timepiece in the world.

Rumor has it the uncarved lump behind the three famous suffragists is reserved for the first woman president.

This lovely pocket park is one of the most under appreciated in D.C.

The famous abolitionist’s preserved estate is one of Washington's finest monuments to its great Black citizens.

A Civil War fort in the middle of Washington, D.C. has been swallowed by a forest.