Dercum Mountain has some glorious view of the valley and the mountains. Hiking up the mountain can be a bit taxing, but you can also take the Gondolas up to the top and hike down, they also offer lunch packages (there is a fee to take the gondolas). Once you are at the top you can walk down the Schoolmarm trail (3.5 miles) or stay on top a while for some awesome photo opportunities, but the gondolas have limited hours depending on the season. The difficulty depends on which trail you take, the Schoolmarm is pretty flat and easy to hike up or down and would be a seven mile loop (2300 vertical), so be prepared for some steep sections, but otherwise the trail offers some awesome views and a winding descent down the mountain. There are several spin off trails that are steeper and some that are less steep, but either way this is a great area to walk. Be careful as there are cyclists in this area. There are some other areas in Keystone, but many are mainly abandoned ski areas or mountain biking terrain, our best bet is to move into Dillon.