The national park was once a plantation estate.

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

Washington's iconic carousel has a nice piece of Civil Rights history.

Legend has it that President Grant’s frequent drinking in the lobby gave rise to the term “lobbyist.”

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

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

The oldest continuously operating fish market in the United States.

Art deco landmark on the outskirts of Washington, D.C.

Members of Congress have traveled between the buildings on Capitol Hill for a century hidden from tourists, press, and storm clouds.

D.C.'s first central library was born out of a chance encounter with the philanthropist whose name it bears.

The most accurate timepiece in the world.

The remains of Martha, the last known passenger pigeon, serve as a tool to educate about conservation.

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.

Rumor has it the uncarved lump behind the three famous suffragists is reserved for the first woman president.

The actual model from the original "Star Trek" series is now on display at the National Air and Space Museum.

A haunting tribute to pioneering photographer Clover Adams.

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

Largest Roman Catholic church in North America.

The first purpose-built art gallery in the United States is once again open as a center of craft arts.

Fittingly, America's museum of architecture is itself a magnificently designed old building.

During the Industrial Revolution this “Temple of Invention” was full of intricate miniature machines and gadgets.

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

Home to items never before seen by the public.

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