The abandoned ruins of America's first private zoo are open for exploration in the Catskills.

The watery entrance for condemned prisoners heading to the Tower of London is still visible along the Thames.

Formerly the most gerrymandered district in the U.S., it twisted and turned along racial borders.

The whole world in one water tank.

Tiny observatory made big contributions to the study of the Earth's motion.

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

After his presidency, George Washington planned to live only a few blocks from the Capitol building.

The tunnel under the Capitol Building where Congress takes out its trash.

A portal into the bricked up canal that runs through the heart of Washington D.C.

Before Nixon, "watergate" meant canals.

Herbert Hoover's "Brown House" rural presidential retreat was a PR disaster amid the start of the Great Depression.

The rogue roots are gradually consuming some of the historic marble grave markers.

The naval commander’s proudest moment in battle is memorialized in this unique tomb at Arlington Cemetery.

The controversial urban planner who designed Washington, D.C., was buried in Maryland, and can presently be found in Virginia.

People escaping slavery may have hidden inside a corpse vault.

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

The oldest continuously operating fish market in the United States.

There’s a hidden military meme engraved on the World War II Memorial.

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

The only tennis court that falls under the jurisdiction of the central bank.

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

A building shaped like the Army Corps of Engineers logo, because why not?

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

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