This unassuming passageway played a key role in one of the most important events in U.S. history.

"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!”

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

One critic described it as "middle Mussolini, early Ramses, and late Neiman-Marcus." Another called it an architectural "natural disaster."

Home to a vast and influential collection of Shakespeareana.

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

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.

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

A muscular Art Deco monument represents the struggle between regulators and unbridled markets.

A spectacular tribute to statesman and philanthropist Andrew Mellon.

A much-maligned monument to teetotalism.

America's Most Wanted's set resides in this tribute to the history of crime and punishment.

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

An echo chamber with a waterfall wrapped around its base at the Embassy of Canada in Washington, D.C.

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

An unassuming, powerful monument north of the U.S. Capitol bears witness to the resilience of Japanese Americans during a time of grave injustice.

A 1,100-ton train fell through the floor in 1953. Workers got it patched up in just 72 hours.

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

Railroad officials in the early 1900s sought to spare travelers the sight of Roman soldiers’ private parts.

An easily overlooked memorial to a Ukrainian famine-genocide that killed over 4 million people.

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