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

This spectacular track has run continuously since 1882.

A popular rock that acted as a waymarker for American pioneers.

A dangerous narrow-gauge railroad once traced a route through this striking canyon.

When ecosystems collide in the arid Southwest.

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

The highest bridge in America was built for an almost unnervingly small amount of money.

Even in death, he's still your huckleberry.

Take a dip in the world's largest mineral hot springs pool.

Crystal clear lake with a shoreline of travertine located in a Colorado canyon.

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

Strange red rock formations that have been attributed to a higher power for hundreds of years.

This erect, phallic geological spire wasn't always named so domestically.

Air Force Academy Chapel made of 100 identical tetrahedrons works to inspire those of all religions.

Long before guestbooks and hotels, frontier travelers signed their names on this rock face.

One of the greatest heroes of the Titanic tragedy came from humble beginnings to this beautiful home.

A Rocky Mountain city provides a happy ending for a pinto pony and his Brobdingnagian red chair.

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

Overlooking the Colorado Convention Center is this giant sculpture made from thousands of triangles.

A small horde of mythical creatures lurk almost imperceptibly within the museum's wildlife dioramas.

A focal point of in Denver’s skyline for over a century, inspired by a Venetian basilica.

The Denver airport is guarded by a 32-foot-tall sculpture of a demonic horse.

This tea house was a hand-built gift from Boulder's sister city in Tajikstan.

Paranormal experiences in this hotel's room 217 led Stephen King to write "The Shining."