This lonely waterfront memorial to the men of the Titanic was erected by the "Women of America."

A nostalgic bibliographic gem.

A Civil War fort in the middle of Washington, D.C. has been swallowed by a forest.

Fittingly, America's museum of architecture is itself a magnificently designed old building.

A lovely aquatic park built by a one-armed Civil War veteran who made a fortune from lotuses.

A derelict bit of transportation infrastructure hidden in the woods.

A cavernous three-story, 43,800-square-foot basement that was forgotten about for 60 years.

A painfully obvious spy house sits right across the street from the Russian Embassy.

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

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

Franciscan monks created a facsimile of the Holy Land for North Americans who couldn’t afford the trip overseas.

A wondrous old library overlooking the nation's capital.

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

A monument in Washington D.C. marks the spot from which all other roads were supposed to stem.

Enormous piles of historically significant stones, dumped by Congress in a forest, and abandoned for 60 years.

One of the dwarven trees dates back to 1625 and survived the Hiroshima bombing.

This grand gothic brewery has been pumping out suds for over a hundred years.

Home to items never before seen by the public.

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.

This splendid Versailles-inspired mansion has the largest French-style formal gardens in North America.

WWII-era bunkers are hidden under the beaches of this picturesque park, which is still scattered with wartime watchtowers. .

A blend of art, antiquities, and Americana fill this museum, surrounded by whimsical, enchanting gardens.

Enchanting gardens surround a derelict mansion, all hidden in plain sight behind a stone wall.