I'm from New Zealand and we are planning a vacation late September departing and arriving 20 September. Our main itinerary is self drive Denver, Cheyenne, Rapid City, Cody, Yellowstone, Jackson, Salt Lake City. We have 10 days because after Salt Lake City, we drive to a convention in Fresno and we have to be in Fresno on 1 October. We would like to see Aspen, but no itineraries seem to include this as part of this tour from Denver - even as a day trip from Denver. Is it doable or is Aspen a trip of it's own? Can we do Aspen from Denver in a day or is that crazy?