This ancient structure is widely thought to be the oldest intact pyramid in the world.

It might not be the prettiest pyramid in Egypt, but it may be the muddiest.

One of its engravings is believed to be among the first representations of medical and surgical instruments.

The largest known Ancient Egyptian obelisk.

The United States Capitol's former columns still stand.

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

The longest escalator in the Western Hemisphere takes over three minutes to ride down.

The tallest The Church of Jesus Christ of Latter-day Saints temple in the world soars above the Beltway.

The 5.5-mile ring of steel posts around the Capitol Building is one of the largest (and most uniform) of its kind in the world.

Corn-inthian columns with a uniquely American take on neoclassical architecture.

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

"Congress may voluntarily remain in session throughout the summer, in order that our Congressmen may be protected from the intolerable discomforts and dangers of the ordinary outdoor weather!”

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

Architecture lovers won’t stop touching the National Gallery's 19.5 degree marble prow.

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

Home to items never before seen by the public.

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

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

You could be standing at the site of one of D.C.'s most fatal tragedies and not even know it.

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

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

Seemingly unremarkable items like empty sushi trays, chef hats, and freshness stickers are being preserved so future generations can look back on this beloved cultural import.

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

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