This old train trestle and collapsed tunnel once allowed the railroad to negotiate the steep slopes of the Colorado Rockies.

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

A coal fire has been burning underground here since 1896.

A prehistoric rock shelter that's literally in someone's backyard.

Two creeks flow out of either end of this canyon in opposite directions.

The remains of an early 1900s dude ranch that operated until the 1970s.

Hidden high on a remote mountain peak is a humbling and mysterious Vietnam War memorial.

The site of the "Bone Wars" between two rival paleontologists during the dinosaur rush of the 19th century.

An antique narrow gauge railway line still running through the Colorado and New Mexico mountains.

16,500-acre ranch filled with American heritage, geological wonders, and a giant pile of tires is the crown jewel of an intriguing tug-of-war.

A river runs through this remote valley in a very unexpected way.

Unlike most arches, this geological oddity formed in a volcanic dike.

This interpretive path lets you get up close and personal with dinosaur bones.

These decaying bridges 1,000 feet high are a reminder of the skill it took to cross the Colorado Rockies by rail.

In the middle of a suburban Denver neighborhood is a cave that once provided solace for a prominent Ute chief and his family.

The wreckage of a World War II bomber is hidden high in the Colorado wilderness.

The haunted reputation of these abandoned Colorado train tunnels is probably not helped by the terrifying spiked fence.

Colorado's only true geyser is hidden within the San Juan National Forest.

At the tallest peak in Colorado, an electrifying mix of thin air, lightning, and rivalry.

The highest paved road in North America winds its way up Mount Blue Sky in Colorado to an altitude of 14,130 feet above sea level.

This super steep hike ascends 2,000 feet in less than a mile.

Silver in the hills led to the speedy creation of this boom town and a lack of it saw the town abandoned nearly as quickly.

Abandoned silver mine strewn with wrecked and twisted structures.

This spectacular track has run continuously since 1882.