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

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

A celebrity from the late Cretaceous period.

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

A haunting tribute to pioneering photographer Clover Adams.

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

An obscure public service from the U.S. government that redeems burnt, moldy, and soiled old greenbacks.

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

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

A three-story tower of books about Abraham Lincoln is one of the more unusual monuments to the president.

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

A derelict bit of transportation infrastructure hidden in the woods.

There's a 12-foot-tall replica of the Washington Monument hidden under a manhole nearby.

A wondrous old library overlooking the nation's capital.

A tiny piece of the Moon is embedded in this stained glass masterpiece.

Enormous piles of historically significant stones, dumped by Congress in a forest, and abandoned for 60 years.

Long-abandoned trolley tunnels just a mile away from the White House are turning into an art space.

With over 100 jam-packed rooms to explore plus elaborate tea services and events, the Mansion on O Street is a hidden treasure.

Home to items never before seen by the public.

The United States Capitol's former columns still stand.

This bug-eyed water wheel uses the power of the Sun to clean up Baltimore Harbor.

The trials and tribulations of marking Poe's grave.

This free, take-a-book shop seems like a trick but isn't.

The site where Poe "in great distress, and ... in need of immediate assistance" likely died.