An underground magnet for ever-changing street art.

The only boathouse Frank Lloyd Wright ever designed was also the only unbuilt structure in his famous Wasmuth Portfolio, until 2007.

An unprepossessing stone marks the last resting place of one of the most accomplished Native Americans in history.

A bas relief commemorates the "Nuns of the Battlefield" who cared for soldiers on both sides of the conflict.

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

Bar full of oddities, specimens, artifacts and homages to the great dime museums of the past.

The beloved statue at the National Academy of Sciences is oh so inviting to sit on.

The rooster who crossed the road lives on forever in Takoma Park, Maryland.

This unique historical monument features large concrete spheres designed to resemble fallen stars.

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

Walk a trail through a historic Quaker town that outlawed slavery in 1777 and was a major waypoint on the Underground Railroad.

This restored log building was one of the first toll booths for travelers along the Northern Turnpike.

An almost life-sized elephant named Ms. Ellie greets visitors at this jumbo-themed museum.

A museum commemorating the Donora Smog, which killed 20 people in October 1948 and sparked national outrage over air pollution.

The Grand Ole Opry's big voice came from a small home in rural Virginia where she was eventually buried.

A pyramid commemorates the birthplace of James Buchanan, the 15th president of the United States

This Art Deco service station has been providing tune-ups and turning heads for close to a century.

This four-story steel sphere in Maryland was used to test biological weapons.

An occult-y, historic hotel with the World's Largest Ouija board on the roof.

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

An astounding collection of medical specimens, including bits of President Lincoln.

A memorial to a shareholder activist feared by CEOs around the United States.

These abandoned waterworks are crumbling into the Potomac River.

Washington's top-secret Cold War-era doomsday communications tower is located in a small neighborhood park.