Take a day or two and drive to Aspen. We went the long way on Independence Pass and the views were mind blowing. The section between Vail and Leadville were nice but the sections from Leadville to Aspen were spectacular, especially in the fall when all the leaves are changing. This drive was one of the highlights of our trip and we stopped several times along the road to take in the views.
Be careful to check if the road is open. The road closes for the winter as soon as the snow starts piling up in the mountains. Try and imagine taking a snow plow up the tight mountain switch backs and you can understand why they close it. There are some bare knuckle moments even in perfect weather on this road so pay attention and stop to look.