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

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

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

The span is crooked and made from two older recycled bridges.

The Conduit Road Schoolhouse is one of the last one-room schoolhouses remaining in Washington, D.C.

A derelict bit of transportation infrastructure hidden in the woods.

Once a sewer culvert, this road tunnel now offers cyclists and pedestrians a subterranean stroll under the C&O Canal.

This nine-story building is the oldest standing skyscraper in D.C.

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

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

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

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

Where the U.S. government kept its actual treasure, before Fort Knox.

Legend has it that President Grant’s frequent drinking in the lobby gave rise to the term “lobbyist.”

The naval commander’s proudest moment in battle is memorialized in this unique tomb at Arlington Cemetery.

Soldiers were buried next to Lee's house in the center of Arlington Cemetery to dissuade the general from reclaiming his property after the war.

The controversial urban planner who designed Washington, D.C., was buried in Maryland, and can presently be found in Virginia.

Born a slave on the Arlington estate, Parks dug the first graves at Arlington National Cemetery, and was buried there, too.

The Pentagon sits on a former island that was in Virginia at low tide and D.C. at high tide.

Please don’t anchor your boat onto the Department of Defense’s underwater data cables.

The 72-foot giant escaped confinement in a large patch of mulch only to be reburied in the sandy shores of the Potomac River.

A cavernous three-story, 43,800-square-foot basement that was forgotten about for 60 years.

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

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