Keystone Mountain Biking
The Keystone Bike Park has spent the time and resources necessary to now be rated among the very best in North America! Take the high-speed River Run gondola to the top of Keystone Mountain (11,600 feet) and then choose Beginner, Intermediate, or Advanced trails down. Because it has the longest drop of any mountain bike park in the country (2,360 vertical feet), you can easily enjoy a half hour of blood-pumping biking on each trip down. In total, Keystone has a 55-mile network consisting of over 50 trails filled with rock ledges, 15-foot jumps, ramps, bridges, and an elevated, 20' woodbridge corkscrew dropline. There are always alternate routes for the less experienced, so everyone can enjoy world-class trails and the artistry of expert bikers without the pain. To truly appreciate this activity, view videos, still photos, and trail maps from Keystone Resort here.
Summit County Bike Path
The Summit County is a 100-mile network of paved paths along streams and around Lake Dillon from Keystone to Dillon, Frisco, Breckenridge, Copper Mountain, then over Vail Pass to Vail and Avon. Or, for a less exhausting alternative, check out Mountain View Sports or call (800) 530-3836 to sign up for their 'Ride the Pass' shuttle service. They will haul an entire group of bikes to the top of Vail Pass, then you can coast all the way down (along a mountain stream) through Copper Mountain to Frisco. From there you can either shuttle back or continue on the mostly flat bike path around Lake Dillon, then through the River Course at Keystone along the Snake River, winding up at the Mountain View Sports shop (between River Run and Keystone Village).
Also review the challenging tours at Colorado Bike and Ski, offering unique outdoor adventures for the entire family - special needs accessible. While you're on their website, check out their recommendations for Day Trips from Summit County if you want to see more of Colorado.