This historic lighthouse was well known for the large number of women who served as its keeper.

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

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

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

A haunting exhibit in a wildlife refuge center highlights threatened species and the conservation efforts needed to save them.

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

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

A priceless collection of the Nation's cryptologic history.

The land is home to swimming ponies and a legendary 18th-century treasure.

Rediscovered after a century, the father of the American Navy was reinterred in something dredged up from Davy Jones' Locker.

The oldest military monument in the United States.

A museum dedicated to exhibiting remarkable outsider art.

One of the last mosaic tile facades found in the city.

An echo chamber with a waterfall wrapped around its base at the Embassy of Canada in Washington, D.C.

The National Park Service’s best-kept secret with views that rival any in D.C.

A 1,100-ton train fell through the floor in 1953. Workers got it patched up in just 72 hours.

A hidden passageway now marks the site of an assassination attempt on Ronald Reagan that some say broke a 140-year-old curse.

A derelict bit of infrastructure from the canal that once ran through D.C. is landlocked in the heart of the city.

A muscular Art Deco monument represents the struggle between regulators and unbridled markets.

While most wind tunnels test scale models, the "Cave of Winds" was large enough for actual airplanes.

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

Look closely and you’ll notice that the color changes a third of the way up the tower.

Architecture lovers won’t stop touching the National Gallery's 19.5 degree marble prow.

A much-maligned monument to teetotalism.