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

A house carved into a rock in the 1940s.

Few things look more out of place than the electric blue ponds in the reddish-brown desert of Utah.

This raised bulls-eye visible from space was the subject of an intense geologic controversy.

One of the world’s largest collections of petroglyphs records 2,000 years of human activity.

The marker offers a rare chance to be in four U.S. states at once, though there's some controversy over its geographic accuracy.

This memorial pays homage to Pueblo's four Medal of Honor recipients.

This historic stone barn is the former home of legendary cattleman Charles “Lonesome Dove” Goodnight.

Inside this casino, visitors are treated to slot machines and a rare German Christmas pyramid.

The largest self-built castle in the U.S., six decades in the making.

The fifth-longest natural arch in the world, and the longest outside China.

The remnants of the base where US Army troops learned how to fight in extreme conditions.

Each year, teams of the world's best snow sculptors have 65 hours to create frozen masterpieces.

While most of the games in this arcade take quarters, that would have been a small fortune when they were made.

The spot in the Mile-High City that's exactly 5,280 feet above sea level (at least for now).

A downtown park built on top of unclaimed graves.

These faux-cliff dwellings allow visitors to climb around on a replica archaeological site.

This natural wonder is disappearing at an alarming rate.

This three-mile concrete levee in Pueblo, Colorado was transformed into the world’s longest painting.

Climb to the top of this spiritual tower, and you'll be rewarded with spectacular views.

This grand stone tower was dedicated to a famed American humorist almost by coincidence.

A mental health hospital dating back more than 139 years, now features a museum.

A futuristic hovertrain is parked unceremoniously alongside a nondescript road.

There are eight natural springs around town, each with a slightly different taste.