We did not bike to the Maroon Bells, but there were lots of bikers on road to the Maroon Bells.  The road [click for a map] is  about 10 miles and gains 1900 feet.  The first 4 miles gain 500 feet, the next 3 another 500 and the last 3 gain 900 feet. The grades work out to 2.5, 3.3 and 6 percent.  But the ascents are very uniform.  I would rate the traffic as heavy, but the drivers were quite considerate of the bikes, and the bikers we talked to said the traffic was no problem.  During the summer months (June through Labor day) cars are not allowed on this road - day tourists must use busses - but campers and many other special users are allowed.  There are quite a few other options for good biking around Aspen.

We hiked up to Crater Lake - about 4 miles round trip with about 800 feet ascent.  The hike is very nice through an aspen forest and the views along the way are great.  The destination is not very interesting - the lake is almost dry.  It's probably very pretty in early season, but it tends to drain, apparently, because it sits in a valley with a porous floor.

View south up the Pyramid Peak valley:

View down the Maroon Lake valley:

The aspens:

A secluded lake in the Colorado Rockies:

A seed pod: