The "Key of Keys" for Washington, D.C. and the apocryphal landing place for the military campaign that started George Washington's career is now at the bottom of a well.

This small hilltop church weaves the urban history of Washington, D.C. with the national history of the United States.

A rare example of a rural school in Washington, D.C.

A street in front of NASA's D.C. headquarters has been named in honor of the Black women who were essential to early spaceflight.

A brass and marble scale model of the solar system embedded in the concrete.

A striking memorial to the 21 lives lost in an explosion at the Washington Arsenal

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

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

Atop this media building, two hives containing more than 30,000 bees keep the surrounding area vibrant.

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

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

A small token of gratitude from freezing cold journalists who were given a warm haven while covering JFK's inauguration.

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

"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!”

The early data processor factory founded in Washington for the 1890 U.S. Census went on to become IBM.

This unassuming passageway played a key role in one of the most important events in U.S. history.

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

A tiny monument to the unsuccessful attempt by Thomas Jefferson to place the prime meridian in Washington.

Before Nixon, "watergate" meant canals.

A diminutive plaque recalls the treetop sniper who almost killed Abe Lincoln.

Go take a picture with the inventor of the daguerreotype photographic process.

This robust fence in front of a historic Georgetown home is likely made from hundreds of recycled Revolutionary War firearms.

The first presidential bomb shelter was located in an old vault under the Treasury, connected to the White House via tunnel.

Senators used to relax in the nearly forgotten marble tubs now hidden in the U.S. Capitol Building's basement.