Carnivorous plants, medieval aphrodisiacs, and the largest original wood structure glass conservatory in the western hemisphere.

In all of the 29 years it was in operation, no prisoners ever escaped successfully... or so they claim.

An organ located deep within a cave, whose "pipes" are the geological features of the cave itself.

This war hero's old shop remembers the fine line between medicine and quackery during the Revolutionary War.

The Kirkland Monument remembers a selfless Civil War hero who braved the battlefield to give water to his dying enemies.

The rogue roots are gradually consuming some of the historic marble grave markers.

Soldiers were buried next to Lee's house in the center of Arlington Cemetery to dissuade the general from reclaiming his property after the war.

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.

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

Home to items never before seen by the public.

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

A traveling postal dog covered 48 states and more than 140,000 miles, and he lives on as taxidermy, patched up with a rabbit's foot and a pig's ear.

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.

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

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

This stunning blue and gold room changed cities twice before becoming part of the Smithsonian.

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

A celebrity from the late Cretaceous period.

The site of the climactic scene from the classic horror film is now a historic landmark.

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

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

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