A labor of love built by local hang-gliding enthusiasts, this ideal launch spot was outlawed by the authorities and has since been largely abandoned.

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

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

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.

The walls of the iconic dome are hollow and have a secret stairway.

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

This statue of the "father of television" stands prominently in the United States Capitol.

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.

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

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

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

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

A hidden gem on the lawn of the U.S. Capitol Building designed by landscape architect Frederick Law Olmsted.

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

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

A much-maligned monument to teetotalism.

The unique traffic pattern named for an influential urban planner is also known as the Pedestrian Scramble.

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.

This English-inspired Maryland garden is home to acres of opulent plant life including bushes shaped into an entire fox hunt.

This bug-eyed water wheel uses the power of the Sun to clean up Baltimore Harbor.

A museum dedicated to exhibiting remarkable outsider art.

Once America's tallest structure, now a Baltimore landmark.

A hidden alley in urban Baltimore is a haven for graffiti artists.