If you want to take valygrl's advice to the max, go to the San Juan mountains in the southwest corner of the start. Make a loop starting with Durango to Ridgway. Then either continue north to Montrose, east a bit, and south through Lake City and Creede. Close the loop over Wolf Creek pass. But that is too far for three days. A shorter loop goes west past Telluride and Cortez. That's probably still too far for three days, so you could just make an out-and-back from Durango to Ouray. Around there you'll see some of the best concentration mountain scenery in the state that you can see from paved roads.