A portal into the bricked up canal that runs through the heart of Washington D.C.

For 60 years, the academy had no permanent location until members voted Washington D.C. as its forever home.

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.

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

The country's oldest continually-operated mini golf course lies hidden in plain sight, eclipsed by one of D.C.'s most popular tourist attractions.

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

The span is crooked and made from two older recycled bridges.

The little-known, 300-year history of the area includes former lives as a bustling tobacco port, parking lot, and industrial dump.

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

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

An overlooked memorial honoring the local Washington residents who died in World War I.

A derelict bit of transportation infrastructure hidden in the woods.

A cavernous three-story, 43,800-square-foot basement that was forgotten about for 60 years.

The only National Monument ever to go missing for nearly 50 years then resurface in a dump.

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

The national park was once a plantation estate.

This forgotten boat elevator was an engineering marvel in its heyday.

This unique historical monument features large concrete spheres designed to resemble fallen stars.

Parking garage where Bob Woodward met Watergate source "Deep Throat."

Please don’t anchor your boat onto the Department of Defense’s underwater data cables.

Amid the sprawling Defense Intelligence Agency Headquarters is one of Washington's least accessible museums.

Volcanic stone sentinels stand watch at a Korean Bell Garden in Virginia.

The Pentagon sits on a former island that was in Virginia at low tide and D.C. at high tide.

This lovely picnic spot featuring thunderous jet landings is an aircraft spotter’s dream.