This abandoned asylum was once a state of the art facility before devolving into one of the most deadly mental institutions in American history.

Remnants of a storybook amusement park hidden behind a strip mall.

The ruins of an 18th-century mansion that was once named "Mistake" by the man who had it built.

This advertisement for talcum powder was painted on the rock face and has since defied removal.

Remains of a historic fountain that was mysteriously lost in the demolition of a D.C. traffic circle.

The childhood home of the Sultan of Swat is just a line drive away from Oriole Park at Camden Yards.

Once a thriving business district, this former shopping area is now an urban ghost town in the heart of the city.

The antique hotel still has a jail in the basement, though the cockfighting ring is long gone.

This ruined quarry once produced the distinctive red sandstone used for construction projects in Washington, D.C.

The Forest Service's surprisingly sophisticated collection of wildfire prevention art features America's most beloved bear.

A star fort along the C&O Canal in western Maryland that protected America in three wars.

America's first nuclear-powered merchant ship is now a time warp to the atomic age.

This fort down the Potomac from Washington, D.C. was once the only defensive fort protecting the capital.

At this former Prohibition speakeasy, electric birds signaled the arrival of hooch.

A remarkable time capsule of American manufacturing deep in Maryland coal country.

This scenic Maryland park was the site of one of the worst prison camps of the Civil War.

This abandoned sea fort has become an accidental bird sanctuary.

Two dozen pinball games hidden away inside a most unlikely location.

The longest escalator in the Western Hemisphere takes over three minutes to ride down.

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

Once part of a dam servicing an early 19th century grist mill, the tucked-way falls are a tricky-to-find urban oasis.

Once home to seven different roller coasters, Glen Echo has undergone many transformations since its founding in 1891.

A model home in the Medical Examiner's Office in which grisly death scenes are staged to train forensic investigators.

A cave on the Maryland border where civilians took refuge during the bloodiest battle of the Civil War.