The Plains of San Agustin are a high, dry, perfectly level basin between the Datil, Gallinas, San Mateo and Magdalena mountains, about 35 miles long and 5 to 15 miles wide. US-60 runs across the northern edge through Datil and Magdalena; from the road the floor of the plain stretches away to the south, almost without features apart from the distant dishes of the Very Large Array. It is one of the most striking landscapes in central New Mexico, particularly at sunrise and sunset when the surrounding ranges throw long colour across the dry lake bed.
The basin is grassland and pronghorn country, with ranches scattered across it and very few buildings of any other kind. Pull-outs along US-60 and the side road south to the VLA visitor centre are the easiest places to take in the scale of the plain. There is no service of any kind on the basin itself — no fuel, no food, no cell signal in most of it — so fill up in Datil or Magdalena before exploring.