This popular tourist cave was ignored for almost 200 years before being mined into an attraction.

The romance of early commercial flight still fills this Art Deco destination.

This isn't your average roadway—it's actually a National Park and a transportation pioneer.

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.

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

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

A much-maligned monument to teetotalism.

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

An office built to look like a giant basket.

An "inside out" building in the historical center of Paris, featuring Europe’s largest modern art museum.

A "haunted" landmark on the coast of Southern California.

North America’s largest collection of horological devices and home to a colossal clock with a dizzying array of features.

This titanic java kettle is one of the many kitschy landmarks located along America's OTHER famous highway.

Frank Lloyd Wright's most iconic home dangles over a Pennsylvania waterfall.

This rare triple-jurisdiction drawbridge passes through Virginia, Maryland, and Washington, D.C.

A lawn full of retired spacecraft on display at one of NASA's first research labs.

Meet some of the most prominent figures in Black history through life-sized wax models.

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

Captain John Smith thought these cliffs were amazing in 1608 but sharks thought so 20 million years before him.

The land is home to swimming ponies and a legendary 18th-century treasure.

Crammed into a Baltimore row house is an oddities shop that sells everything from skulls to dead insects.

This Maryland farm is known for its amazing corn mazes and its 30-foot junkbots.

Aqueducts have dramatically changed this old lake, now home to tufa towers and its very own species of tiny brine shrimp.

Four hundred granite steps were built into this massive rock by the National Park Service.