Downhill Skiing can burn up to 648 calories/hour. It works your glutes, quadriceps, hamstrings, and calves - so the whole leg gets sculpted at the same time. The abs and other core muscles do too.
Cross Country Skiing is even better than that! In addition to working your leg muscles and core muscles (see downhill skiing above), it also helps you build your biceps and triceps because you dont have gravity pushing you down that mountain- you have to pull yourself - your shoulders will get a workout too! Plus you can burn an additional 100 calories/hour to downhill skiing. Either way it is going to be an intense day!