This is Moraine Park located inside Rocky Mountain National Park. According to allrockymountain.com, this area was carved out by glaciers thousands of years ago. I have seen herds of Elk lining this field during mating season. There is a large campground just to the north of this open area, but get your reservations early in the summer as it fills up fast. The winter isn’t as busy, but I would still recommend a reservation on weekends.