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

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

Decades before the scandal, this staircase on the river was a literal "water gate."

A celebrity from the late Cretaceous period.

You could be standing at the site of one of D.C.'s most fatal tragedies and not even know it.

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

The oldest building in the District of Columbia was preserved because of a mistaken connection to George Washington.

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

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

A haunting tribute to pioneering photographer Clover Adams.

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

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

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

Largest Roman Catholic church in North America.

The actual model from the original "Star Trek" series is now on display at the National Air and Space Museum.

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

The national park was once a plantation estate.

There’s a hidden military meme engraved on the World War II Memorial.

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

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

The beloved statue at the National Academy of Sciences is oh so inviting to sit on.

A derelict bit of transportation infrastructure hidden in the woods.

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

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