The ruins of an old mill lie in a small ravine along a hiking trail near Little Seneca Creek.

America's first federal monument.

An astounding collection of medical specimens, including bits of President Lincoln.

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

This colonial tavern played host to George Washington, Thomas Jefferson, and other famous early Americans.

This isn't your average roadway—it's actually a National Park and a transportation pioneer.

A celebrity from the late Cretaceous period.

The site of the climactic scene from the classic horror film is now a historic landmark.

Home to items never before seen by the public.

A traveling postal dog covered 48 states and more than 140,000 miles, and he lives on as taxidermy, patched up with a rabbit's foot and a pig's ear.

Those with a sharp eye can find the hidden image of a German Shepherd on the memorial's Mural Wall.

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

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

A much-maligned monument to teetotalism.

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

Look closely and you’ll notice that the color changes a third of the way up the tower.

One of the most influential presidents in U.S. history wanted only this plain, elegant monument as his lasting memorial.

Perhaps the most scandalous statue of America's first president.

A derelict bit of infrastructure from the canal that once ran through D.C. is landlocked in the heart of the city.

Go take a picture with the inventor of the daguerreotype photographic process.

This restaurant has been a haven for D.C.'s LGBTQ community since the 1950s.

The 340-year-old house that inspired the classic Nathaniel Hawthorne novel.

The lecture hall where Alexander Graham Bell first demonstrated the long-distance phone call.

Statue in Salem of the woman who starred as the witch Samantha in the sitcom "Bewitched."