Atsinna was a pueblo built in a defensive position atop Inscription Rock at what is now El Morro National Monument. The pueblo was only occupied for about 75 years, from about 1275 to about 1350 CE. In those days the location was along the boundary between the Mogollon people to the south and the Ancestral Puebloans to the north. Whoever they may have been, the residents of Atsinna built an 875-room pueblo that was occupied by up to 1,500 people at its height. Atsinna was the largest pueblo built on top of El Morro Rock.
Today, there is a paved 1/2 mile trail leading from the parking area to the pool of water at the foot of the cliff. If you have more time to explore, the 2-mile trail (includes the journey to the pool and past the inscriptions) to the top of the sandstone bluffs (250 feet of elevation gain) is well worth the hike for the views alone, never mind the chance to visit the ruins of Atsinna. While you're climbing the trail, keep in mind that for 75 years, the ancients sometimes carried water up this hill to Atsinna. They made pottery to carry and store the water.
Atsinna was settled in the time of the Mogollon peoples migrations out of the Gila Mountains and the Mimbres River Valley. The location is about halfway between the pueblos of Acoma and Hawikuh (Zuni). The abandonment of Atsinna also coincides pretty closely with the founding of Pottery Mound to the east.
In one of the kivas excavated at Atsinna a polychrome geometric wall mural was found. That mural was dated to have been painted between 1275 and 1300 CE, before the founding of Pottery Mound.
Today's Zuni consider Atsinna and its immediate neighbors to have been outlying villages of their people back in the day. There was a short-lived migration from Zuni to Acoma and then to Pottery Mound between 1395 and 1415. Then Pottery Mound was abandoned, the out-migration beginning around 1475 and by 1500, everyone had gone back to wherever their families had come from.