Aztec Ruins, built and used over a 200-year period, is the largest Ancestral Pueblo community in the Animas River valley. Concentrated on and below a terrace overlooking the Animas River, the people at Aztec built several multi-story buildings called “great houses” and many smaller structures. Associated with each great house was a “great kiva”—a large circular chamber used for ceremonies. Nearby are three unusual “tri-wall” structures—above ground kivas encircled by three concentric walls. In addition, they modified the landscape with dozens of linear swales called “roads,” earthen berms, and platforms.