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

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

Art deco landmark on the outskirts of Washington, D.C.

The only Civil War battle in Washington D.C. took place near this highest natural point in the city.

The remains of Martha, the last known passenger pigeon, serve as a tool to educate about conservation.

The most accurate timepiece in the world.

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

A celebrity from the late Cretaceous period.

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

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

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

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.

The oldest continuously operating fish market in the United States.

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

The winding route passes through an enclosed alleyway, two tunnels, and leads to the White House basement.

A derelict bit of transportation infrastructure hidden in the woods.

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

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

Home to items never before seen by the public.

Also known as "Robin Hood's tree," this tree became a famed location along Hadrian's Wall before it was cut down in an act of vandalism.

A former major munitions plant that has been converted into a sprawling art space.

This brick-lined pedestrian walkway was once a railway tunnel used during the Civil War.

This rare triple-jurisdiction drawbridge passes through Virginia, Maryland, and Washington, D.C.