The Plains of San Agustin form a broad high-desert basin in southwestern New Mexico, enclosed by mountain ranges and shaped by major geologic forces. This graben subsided thousands of feet between parallel faults, and its unusually flat floor was later formed by ancient Lake San Agustin during the last glacial period. An endorheic landscape, it gathers runoff into terminal playas rather than draining to the sea. Near the northern edge of the Chihuahuan Desert, the plains are also known for archaeological and historic sites around their margins. Today, their isolation and surrounding mountains make them the home of the Very Large Array, linking geology, archaeology, and modern science in one distinctive landscape.