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.

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

Home to a vast and influential collection of Shakespeareana.

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

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

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

A hidden passageway now marks the site of an assassination attempt on Ronald Reagan that some say broke a 140-year-old curse.

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

Every drop of D.C. tap water flows through this old waterworks.

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

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

A diminutive memorial marks the site of a successful assassination by a right-wing death squad in America's capital.

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.

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

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

"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!”

Before Nixon, "watergate" meant canals.

A historic arena where the Beatles played their first concert in the U.S.

An easily overlooked memorial to a Ukrainian famine-genocide that killed over 4 million people.

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

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

This stunning blue and gold room changed cities twice before becoming part of the Smithsonian.

The unique traffic pattern named for an influential urban planner is also known as the Pedestrian Scramble.