The most accurate timepiece in the world.

A super-sized promotional trick that is now a D.C. landmark.

Largest Roman Catholic church in North America.

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

The oldest continuously operating fish market in the United States.

A museum cafe showcases Native American dishes and indigenous ingredients from across the Western Hemisphere.

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

This grand gothic brewery has been pumping out suds for over a hundred years.

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

One of the dwarven trees dates back to 1625 and survived the Hiroshima bombing.

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.

The United States Capitol's former columns still stand.