I would also suggest Glenwood Springs. First of all, there is the large hot springs and spa. Secondly, the bike/pedestrian trail up the canyon is not to be missed. You will see it from across the river from the train, but the best view - with the ability to stop when you want - is to be had on the trail. It is paved all the way, and in the vicinity of 12 miles each way if I remember correctly. So a fairly easy bike ride. You can rent bikes in downtown Glenwood Springs. One of the stopping points on the trail is the trailhead up to Hanging Lake. This is for hiking only, but pretty spectacular. Last time I was there, I biked the canyon trail and did the climb to Hanging Lake. Terrific views from the trail as it winds around mostly under I-70. You can see the train track on the other side, including the Zephyr going by if you time your bike/hike right.
