 I @-@ 70 exits the valley through De Beque Canyon , a path carved by the Colorado River that separates the Book Cliffs from Battlement Mesa . The river and its tributaries provide the course for the ascent up the Rocky Mountains . In the canyon , I @-@ 70 enters the Beavertail Mountain Tunnel , the first of several tunnels built to route the freeway across the Rockies . This tunnel design features a curved sidewall , unusual for tunnels in the United States , where most tunnels feature a curved roof and flat side @-@ walls . Engineers borrowed a European design to give the tunnel added strength . After the canyon winds past the Book Cliffs , the highway follows the Colorado River through a valley containing the communities of Parachute and Rifle . 
