Four bald cypress trees in Lafayette Square, across from the White House, mark the southern edge of a 100,000 year old cypress swamp.

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

These recently uncovered walls are all that's left of Washington, D.C's first defense contractor.

A brass plaque dedicated to a convicted cannibal hangs in the National Press Club, and that's not even the craziest part of the story.

A hoard of sky catalogs, astrophysical journals, even the works of Galileo and Copernicus.

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

Obscure Freemasons still live in D.C.’s largest private residence.

A computer bug so primitive it was an actual insect.

The hidden offices underneath Memorial Bridge have been locked up since 1976.

Home to a vast and influential collection of Shakespeareana.

The house where John Wilkes Booth conspired with his co-conspirators.

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

An atomic bomb-proof strongbox protects the U.S. Constitution from terrorists and thieves.

This imposing Masonic temple a mile from the White House was the first public library in Washington, D.C.

There's a crumbling old mansion inside the Smithsonian National Zoo.

The famous abolitionist’s preserved estate is one of Washington's finest monuments to its great Black citizens.

The first purpose-built art gallery in the United States is once again open as a center of craft arts.

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

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

A Spiritualist house of worship where believers communicate with the dead in the spirit world.

When it opened during the final years of the embargo, all the drinks and cigars were free.

A rotating cast of guys and dolls in front of a Washington, D.C. building.

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

The national park was once a plantation estate.