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

Home to items never before seen by the public.

While most wind tunnels test scale models, the "Cave of Winds" was large enough for actual airplanes.

The "lovely red Vega" of the legendary record-settling pilot.

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

An atomic bomb-proof strongbox protects the U.S. Constitution from terrorists and thieves.

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

The 28,000-year-old specimen is remarkably intact.

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

The monument's pointy aluminum tip has been melted down by repeated lightning strikes.

Daredevil repair workers can worm their way out the access hatch, loop ropes over the apex and rappel down the monument.

Perhaps the most scandalous statue of America's first president.

Look closely and you’ll notice that the color changes a third of the way up the tower.

This mysterious structure by the Washington Monument is a flood barrier designed to protect the White House against rising waters.

The preamble to the U.S. Constitution written entirely from vanity license plates hangs in the Smithsonian museum.

Light bulbs, scrap wood, and tinfoil comprise this homemade throne of the gods.

This seemingly out-of-place gas station by the Watergate hotel was once described as the most expensive gas station in the world.