It's so easy it's like riding a bike! Seeing the Aspen area via bicycle is quite spectacular and you don't have to be a pro to do so. Check out one of Aspen's many bike shops and rent a cruiser for a jaunt around town or down the Rio Grande Trail, or take it up a notch for road biking. It might just be one of the best ways to explore the Maroon Bells area and Castle Creek Valley. For those who enjoy off-road adrenaline, mountain bikes are also available and the local trails can't be beat. Smuggler Mountain Road is a gateway to multiple loops such as the Hunter Creek Loop, Iowa Shaft, Tootsie Roll and Lollipop. Check out some bike trails here.
In the central region of the Colorado Rocky Mountains which covers Aspen, Snowmass Village, Basalt, Carbondale, Glenwood Springs and Rifle there are plenty of easy, paved trails for leisure bicycling and walking. All of these trails follow creeks and rivers making for small elevation changes and gorgeous scenery! Plus there are many opportunities to stop along the way. Lay Some Tread's website will tell you more!
Aspen is host to several biking events throughout the summer with its very own Aspen Cycling Festival kicking things off in May. This festival includes the ever-popular Ride for the Pass which takes cyclists to the top of Independence Pass prior to the road opening for car traffic for the season. Aspen and Snowmass will also host the Official Start of the 2013 USA Pro Challenge on August 19 and the Stage 2 Start - Aspen to Breckenridge on August 20, 2013 -- the towns will be hosting many events leading up to and during the race, check out the events calednar.