Extending southward from the tri-wall structure are two massive parallel walls made of cobblestones laid in thick mortar, and two more equally massive walls extend westward from these. There are scattered smaller walls, also of cobblestones; while we do not know their original dimensions, they suggest rectangular enclosures which may have contained house rooms of lighter construction. The ruins contained within the Aztec Ruins National Monument constitute a complex of prehistoric remains representative of several different construction periods. Different groups of Indians seemed to have been involved at various times, and only further excavation will fully clarify their relationships. _The Natural Scene_ Aztec Ruins National Monument is located on the Animas River in northwestern New Mexico, about 20 miles below the Colorado State line and 14 miles above the point where the Animas flows into the San Juan. The monument is on the west bank of the Animas on high ground about halfway between the river and the low-lying hills and mesas which border the river valley. The valley, although narrow at spots, is about 2 miles wide at the point where the ruins are located. The floor of the valley is composed of fertile alluvial soil, which produces fine crops if irrigated. Today, as in prehistoric times, the population of this area is concentrated along the river. It was this permanent source of water that induced the builders of the Aztec pueblo, and in later times the white man, to settle this valley. No doubt many of the fields cultivated today are the same ones that were tilled by the original inhabitants of the area. The valley floor and valley terraces are dotted with saltbush, rabbitbrush, greasewood, and sagebrush. The riverbanks and ditches are lined with willows and huge cottonwoods. Cattails and reeds grow in the marshy areas, and wild roses grow in the shady spots. The low hills and uplands bordering the river valley have a sparse cover of vegetation because of the small amount of rainfall. Therefore the main growth is juniper and pinyon. Typical of the Upper Sonoran Life Zone, these small, hardy trees can withstand dry periods and survive in semiarid country. Today much of the valley is under cultivation or in pasture, and the mild and very dry climate is well suited to growing non-citrus fruit. Elevation at the monument is about 5,600 feet above sea level. Average annual rainfall is about 9½ inches; the humidity is usually very low. Temperatures will reach the mid-90’s during July and August, but evenings are cool and pleasant. Night temperatures in the 60’s are not uncommon even after the hottest summer days. Occasional afternoon thundershowers give relief from the heat during late July and August. [Illustration: Skunk.]