When it comes to handsignals (and colonialism) rock always beats scissors.

A hoard of sky catalogs, astrophysical journals, even the works of Galileo and Copernicus.

The most accurate timepiece in the world.

Sit where JFK proposed to Jackie or where Nixon dined on meatloaf at this storied pub.

A small token of gratitude from freezing cold journalists who were given a warm haven while covering JFK's inauguration.

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.

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

Helen Keller once broke ground on this historic center for the study of technologies to benefit the hearing impaired.

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

This historic boathouse was constructed using salvaged lumber from burned barns.

A wondrous old library overlooking the nation's capital.

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

A derelict bit of transportation infrastructure hidden in the woods.

There’s a special club house at the top for the bell ringers.

The sci-fi villain is a little-known inhabitant of the U.S. capital's largest cathedral.

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

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

This poor little statue is the most vandalized memorial in Washington.

The last remaining building in Washington, D.C., built by H.H. Richardson, one of America's most iconic architects.

An amazing example of early-20th-century architecture, this church features marble transported from Utah.

The district's only illusionarium supports free writing programs for local students with every purchase.

Dedicated to the man who created the first radio wave communication system.

An ear-piercing buzzer calls lawmakers to a vote with a series of long and short rings to form coded messages.

A little marble compass above George Washington's (empty) tomb in the Capitol marks where D.C.'s four quadrants intersect.