Eighteen miniature death-scene dioramas.

A historic Maryland home that once belonged to a man who has been called "the most insignificant" U.S. Supreme Court justice.

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

These abandoned waterworks are crumbling into the Potomac River.

A surprising, but overlooked example of geology in the middle of the nation’s capital.

There’s a special club house at the top for the bell ringers.

Before Nixon, "watergate" meant canals.

The only Civil War battle in Washington D.C. took place near this highest natural point in the city.

The span is crooked and made from two older recycled bridges.

These recently uncovered walls are all that's left of Washington, D.C's first defense contractor.

There's a crumbling old mansion inside the Smithsonian National Zoo.

The national park was once a plantation estate.

A rotating cast of guys and dolls in front of a Washington, D.C. building.

This lonely waterfront memorial to the men of the Titanic was erected by the "Women of America."

People escaping slavery may have hidden inside a corpse vault.

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

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

A derelict bit of transportation infrastructure hidden in the woods.

A three-story tower of books about Abraham Lincoln is one of the more unusual monuments to the president.

A monument in Washington D.C. marks the spot from which all other roads were supposed to stem.

Fittingly, America's museum of architecture is itself a magnificently designed old building.

With over 100 jam-packed rooms to explore plus elaborate tea services and events, the Mansion on O Street is a hidden treasure.

Long-abandoned trolley tunnels just a mile away from the White House are turning into an art space.

Franciscan monks created a facsimile of the Holy Land for North Americans who couldn’t afford the trip overseas.