An Industrial Revolution-era public work that purified water using nothing but sand.

The only female equestrian statue in Washington, D.C. is a 15th-century French heroine.

The revival of a classic Art Deco theater.

Dedicated to the man who created the first radio wave communication system.

The only Leonardo Da Vinci painting in the Western Hemisphere.

The hippo that stands on this university campus was once a drunken flea market purchase.

Washington D.C.'s most famous pianist, composer, and bandleader still tickles the ivories outside Howard Theater.

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

The legacy of a wealthy executive and his wife, this little-known art museum features works by Picasso, Monet, Renoir, Cezanne, and more.

The story behind this beloved toy—named for Theodore Roosevelt and owned by his grandson—is more complicated than you might guess.

Garments from across the globe call this hidden gem home.

This statue of the "father of television" stands prominently in the United States Capitol.

Coins and medals straight from the mint await visitors to this shop in the nation's capital.

Press 1 for knock-knock jokes.

The National Park Service’s best-kept secret with views that rival any in D.C.

An ear-piercing buzzer calls lawmakers to a vote with a series of long and short rings to form coded messages.

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

This groundbreaking 16th-century map is known as "America's birth certificate."

This grisly headstone doesn’t seem to be resting in peace.

A public art jibe at one of the United States’ oldest and longest-serving senators.

During Prohibition, the U.S. Congress had an "official" bootlegger, with his own Capitol Hill office.

More than 500 unique and specially designed cases collected by D.C.'s "Harmonica Case Man."

Helen Keller once broke ground on this historic center for the study of technologies to benefit the hearing impaired.

They sort through millions of dollars worth of diplomatic gifts on behalf of the government.