An immersive environment that is part haunted house, part choose-your-own-adventure, and part jungle gym.

A multi-storied adobe complex has been inhabited for more than a thousand years.

America's only nuclear missile silo open to the public.

One of nature's most well-scheduled phenomenons resides in Wyoming's Yellowstone National Park.

The history of radiation is on safe display at the foot of a radiation science laboratory.

Dyed by iron oxide over centuries, these sandstone rocks rise thousands of feet into the sky.

This iconic 1958 tower welcomes air travelers to Tucson with neon-lit letters and architectural style.

Legend says train robbers stashed their gold within the depths of this unusual cave.

In Tucson a giant metal snake helps pedestrians cross a busy highway.

The world's largest military aircraft cemetery.

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

This 4,000-foot-diameter hole is touted as "the most well known, best preserved meteorite crater on Earth."

The largest hot spring in the United States is, as the name suggests, a stunning show of natural color.

A beautiful geyser under environmental threat.

The vast, legendary catacombs hold secrets much stranger than stacked bones.

Secret refuge and museum of the Duke of Florence.

Over 50 exquisite hand-painted Renaissance maps decorate a Medici storage room.

A copy of the famous statue can be found in this Florence piazza, along with one of the most breathtaking views of the city below.

The graveyard is filled with beautiful funerary art and boasts breathtaking views of Florence.

This demon atop the Notre-Dame de Paris looks utterly bored.

The home where a lovestruck Fitzgerald wrote his first published novel, "This Side of Paradise."

These crudely shaped folk giants may be the the second most photographed statues in the U.S.

The only arched bridge made of stone on the entire Mississippi River.

At this Minnesota state park you can easily wade across the source of the mighty Mississippi.