Glenwood Canyon

The Colorado River runs for about twelve miles through Glenwood Canyon between Dotsero and Glenwood Springs, and the railroad has followed it since the 1880s. When Interstate 70 came, engineers had nowhere to put four lanes except on the canyon's walls. The design they settled on stacked the eastbound and westbound lanes at different heights on cantilevered viaducts and retaining walls, bored the Hanging Lake and Reverse Curve tunnels, and kept the river, the rails and a bike path beside it. The canyon segment opened in 1992, among the last pieces of the interstate system to be finished.

In August 2020 the Grizzly Creek Fire burned more than 30,000 acres of the canyon's slopes. The next summer heavy rains brought mud, boulders and burned timber down the bare gullies onto the highway again and again. On July 29, 2021, debris flows buried stretches of I-70 within minutes; twenty-nine stranded drivers spent the night sheltering in the Hanging Lake Tunnel's operations complex, and the interstate stayed closed for about two weeks, with detours adding hours between Denver and Grand Junction.

Hanging Lake, which Glenwood Springs bought in 1912, sits at the top of a steep trail of a little over a mile from the canyon floor, a travertine-rimmed pool fed by waterfalls over a ledge. Crowds were damaging it badly enough that a permit and shuttle system began in 2019. The 2021 flows muddied the lake and wrecked the trail's bridges; the trail reopened after repairs, and every one of its seven bridges over Deadhorse Creek has since been replaced. A permit is still required.