During the Industrial Revolution this “Temple of Invention” was full of intricate miniature machines and gadgets.

The country's oldest continually-operated mini golf course lies hidden in plain sight, eclipsed by one of D.C.'s most popular tourist attractions.

A hidden gem on the lawn of the U.S. Capitol Building designed by landscape architect Frederick Law Olmsted.

Home to items never before seen by the public.

The site of the climactic scene from the classic horror film is now a historic landmark.

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

The United States Capitol's former columns still stand.

A girls' boarding school inspired by the Chicago World's Fair, once abandoned, now restored to strange and scenic glory.

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

She stares out across six lanes of traffic, clutching a musket and infant with determination.

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

The tallest The Church of Jesus Christ of Latter-day Saints temple in the world soars above the Beltway.