This valley just outside Leadville, Colorado was the training location for the 10th Mountain Division of the United States Army. It's 9300 foot elevation was selected because of it's abundance of snow and was used to train soldiers for winter survival and snow skiing. The camp had the ability to house more than 15,000 soldiers. It is now managed by the U.S. National Forest Service.Photo: ricardoreitmeyer / iStock / Getty Images