The home of the artist credited with introducing the tomato to the American diet.

A single light illuminates one man's overshadowed contributions to street lamp history.

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

Literal "money laundering."

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

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

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

The school tested mustard gas for the U.S. Army during World War I.

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

An obscure public service from the U.S. government that redeems burnt, moldy, and soiled old greenbacks.

In the basement of the U.S. Capitol Building is a hidden storage room full of ornate floor tiles leftover from the 1850s.

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

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

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

A historic estate packed with George Washington's heirlooms, and its own nuclear bunker.

An obscure federal monument honors the French diplomat who served as Ambassador to the U.S. during WWI.

There's an old indoor swimming pool hidden directly underneath the White House Press Briefing Room.

The elevator that makes it possible to fly American flags in bulk over the U.S. Capitol

Before Nixon, "watergate" meant canals.

Need a hardcopy of the 50-title Code of Federal Regulations? This is the place.

The iconic D.C. restaurant where the Cuban Missile Crisis was negotiated, now a Walgreens.

Before Metro, Washington had a robust streetcar network—and you see the remains of this infrastructure if you know where to look.

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

The monument's pointy aluminum tip has been melted down by repeated lightning strikes.