This stately mansion, built in 1787 by America's first Secretary of the Navy, is rumored to be one of the most haunted buildings in Washington, DC.

Before Metro, Washington had a robust streetcar network—and you see the remains of this infrastructure if you know where to look.

This robust fence in front of a historic Georgetown home is likely made from hundreds of recycled Revolutionary War firearms.

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

People escaping slavery may have hidden inside a corpse vault.

Once a sewer culvert, this road tunnel now offers cyclists and pedestrians a subterranean stroll under the C&O Canal.

The first museum in the U.S. to address human rights issues in China.

A brass and marble scale model of the solar system embedded in the concrete.

A wondrous old library overlooking the nation's capital.

A terrace reminiscent of Rome's Spanish Steps is tucked away in a little park in Washington, D.C.

A derelict bit of transportation infrastructure hidden in the woods.

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

The only female equestrian statue in Washington, D.C. is a 15th-century French heroine.

This poor little statue is the most vandalized memorial in Washington.

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

Mysterious installations bring levity and light to a sometimes stodgy city.

A building shaped like the Army Corps of Engineers logo, because why not?

The last remaining building in Washington, D.C., built by H.H. Richardson, one of America's most iconic architects.

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

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

A museum dedicated to Latvian history in the heart of Maryland.

Giftshop catering to cryptozoologists and anyone with a sense of humor.

The district's only illusionarium supports free writing programs for local students with every purchase.

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