A former Confederate hospital serves as a remembrance of wounded and dead soldiers.

Before founding the American Red Cross, Clara Barton had a tremendous humanitarian impact by locating thousands of missing soldiers.

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

The first presidential bomb shelter was located in an old vault under the Treasury, connected to the White House via tunnel.

A three-story tower of books about Abraham Lincoln is one of the more unusual monuments to the president.

Cold War intelligence agents monitored communist embassies from an attic in a former pigeon coop.

This stunning blue and gold room changed cities twice before becoming part of the Smithsonian.

Government testing at the asylum briefly explored using marijuana as a "truth serum" on Nazi prisoners of war.

D.C.'s first central library was born out of a chance encounter with the philanthropist whose name it bears.

Housing the National Women's Party since 1929, this historic house is now a monument to the fight for gender equality.

It was once the base for a series of domestic terror attacks.

The Byzantine, pre-Columbian, and medieval art at this stately mansion are some of the most under-appreciated collections in D.C.

This leafy estate is worth $18 million and is so grand it has two mailing addresses.

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

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

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

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

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.

The United States Capitol's former columns still stand.

The iconic statue was moved to a new spot overlooking the James river after several years as a mascot for the local baseball team.