New Mexico Highway 4 climbs steadily, sometimes steeply, west out of Los Alamos, through forests scorched by wildfire in recent decades, and over a pass at the top of Bandelier National Monument. The road drops slightly then bursts out of the trees. Spread suddenly before us is a vast grassland, the Valle Grande, in Valles Caldera National Preserve, a recent addition to the national park system. This huge meadow seems the bottom of a bowl and we are on its south rim. Eleven miles to the north is the north rim of the caldera, rising to 10,000 feet. The 87,000-acre National Preserve, established in 2000, was placed under the care of the National Park Service in 2015.