Mysterious installations bring levity and light to a sometimes stodgy city.

The ruins of an old mill lie in a small ravine along a hiking trail near Little Seneca Creek.

This abandoned Victorian-style house was built in 1884.

Exact replica of the ancient monument, but much, much lighter.

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

Captain John Smith thought these cliffs were amazing in 1608 but sharks thought so 20 million years before him.

The remnants of a wooden-hulled fleet built and abandoned in WWI, now home to a thriving ecosystem.

This brick-lined pedestrian walkway was once a railway tunnel used during the Civil War.

The oldest building in the District of Columbia was preserved because of a mistaken connection to George Washington.

There's a 12-foot-tall replica of the Washington Monument hidden under a manhole nearby.

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.

The United States Capitol's former columns still stand.

The hidden offices underneath Memorial Bridge have been locked up since 1976.

Standing for over 200 years, the abandoned home of a Revolutionary War hero and later a succession of prison superintendents.

Hidden in the forest atop a long, winding driveway is this stately home.