At Gates of the Arctic National Park and Preserve in Alaska, wild rivers meander through glacier-carved valleys, caribou migrate along age-old trails and endless summer light fades into aurora-lit night skies of winter. It remains virtually unchanged except by the forces of nature. With no roads, getting here is a challenge, but the reward is a lifetime of amazing memories. Photo by Carl Johnson, National Park Service. Posted on Tumblr by the US Department of the Interior, 8/30/16.