You can rent a Jeep to hit the trails, or if you prefer to go on a tour, they have large vehicle Jeep trail tours, too. That's an awesome way to get above the tree line.
There's also horseback riding and chuckwagon dinners. Or you can spend the day soaking in the huge hot springs pool in town. The restaurants are very nice there, too. Hiking, biking, fishing and walks along the Uncompahgre River are great, too.