Keystone Resort: Did you know that Keystone is the largest ski resort in Summit County? Owned by Vail Resorts, Keystone consists of three mountains -- Dercum Mountain, North Peak, and the Outback --  with terrain for skiers and riders of all levels. Five bowls provide plenty of advanced skiing, and you can experience the backcountry by either hiking or paying $5 a ride for snowcat service to the top of the North and South bowls. Keystone is also the largest operation in Colorado to offer night skiing. The best discount lift tickets to Keystone can be found at GetSkiTickets.com!