One of the first hotel rooms in a pod.

This fort down the Potomac from Washington, D.C. was once the only defensive fort protecting the capital.

Two dozen pinball games hidden away inside a most unlikely location.

A tiny monument to the unsuccessful attempt by Thomas Jefferson to place the prime meridian in Washington.

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

A historic arena where the Beatles played their first concert in the U.S.

Was there a small "backpack nuke" hidden in the attic? JFK apparently thought so.

Need a hardcopy of the 50-title Code of Federal Regulations? This is the place.

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.