See massive fossils that are over 200 million years old in northeastern Arizona.

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.

An ear-piercing buzzer calls lawmakers to a vote with a series of long and short rings to form coded messages.

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

A derelict bit of infrastructure from the canal that once ran through D.C. is landlocked in the heart of the city.

This mysterious structure by the Washington Monument is a flood barrier designed to protect the White House against rising waters.

An overlooked memorial honoring the local Washington residents who died in World War I.

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

There’s a hidden military meme engraved on the World War II Memorial.

Sports history, made in the Arroyo Seco.

The world’s largest concentrated solar plant generates as many problems as megawatts.

This 19th century train workshop is a treasure trove of railroad history.

A massive hydrovolcanic explosion left a half-mile wide crater in Death Valley.

A massive volcanic plug is now a protected area that hosts a number of bird species.

This quirky UFO-shaped curiosity is often mistaken for the airport’s control tower.

An abandoned Jazz Age dream home and con man's hideout in Death Valley.

A desert ghost town—occupied for only 12 years—was once home to more than 500 silver mines.

The ghostly remains of an accidental sea.

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

The last moments of the ill-fated Pompeiians, frozen forever in plaster.

A mysterious chasm in the heart of the ancient Roman Forum, the Lacus Curtius was once believed to be a gateway to hell.

A battle between nature and architecture in the Cambodian jungle.

Starship-temple contains 400 tons of drinking water and offers free Japanese lessons.

Go through the looking glass in Tokyo's Wonderland-themed shop.