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

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

Was there a small "backpack nuke" hidden in the attic? JFK apparently thought so.

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

A muscular Art Deco monument represents the struggle between regulators and unbridled markets.

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

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

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

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

The preamble to the U.S. Constitution written entirely from vanity license plates hangs in the Smithsonian museum.

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

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

Before Nixon, "watergate" meant canals.

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

This unacceptably tall building was the real reason for Washington, D.C.'s skyscraper ban.

A much-maligned monument to teetotalism.

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

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

This sandwich shop has a century-old elevator behind a sheet of plexiglass.

The "lovely red Vega" of the legendary record-settling pilot.

A little marble compass above George Washington's (empty) tomb in the Capitol marks where D.C.'s four quadrants intersect.

A museum cafe showcases Native American dishes and indigenous ingredients from across the Western Hemisphere.

An overlooked oasis of quiet on the grounds of Washington's monumental basilica.