The Valles Caldera is a vast circular meadow — 22 kilometres across — formed by a volcanic collapse over a million years ago. The floor of the caldera is a high grassland ringed by forested slopes, and in summer it holds the largest elk herd in New Mexico. The sight of hundreds of elk in a basin surrounded by mountains is one of the more extraordinary things you can see in the American Southwest without leaving the road.
The preserve offers hiking, fly fishing, and guided tours of areas otherwise closed to visitors. In winter, skiing and snowshoeing are available. The entrance is about 15 miles west of Los Alamos on Highway 4, and the drive through the Jemez Mountains is worthwhile in itself.