How was it built?
Father Kino, in 1694, was the first European to call this structure Casa Grande. It is a Spanish word that means 'great house.' The Casa Grande is a 4-story, 11-room structure. It was built around 1350 C.E. and was abandoned about 1450 C.E. It is made of a material called "caliche," which is a type of soil found in the Sonoran Desert. Caliche is a mixture of clay, sand, and calcium carbonate. When it's dry, it is almost as hard as concrete!
Archeologists think the ancient Sonoran Desert people built the "great house" using a technique called "puddling." They would dig a pit in the ground until they reached the layer of caliche and then would fill up the pit with water. The water would help soften the caliche to form a mud with a dough-like consistency. They would then carry the caliche mud in baskets to the construction site and hand-mold it in layers to build up their walls. The Casa Grande is made from about 3,000 tons of caliche. That's about six million pounds!
Why was it built?
What did the ancient Sonoran Desert people use this building for? Maybe it was somebody's home. Some say it was a temple or maybe a watchtower. It might have been a place for storing seeds and food. Others think it was used as an astronomical observatory where they could keep track of the sun, moon, and stars. What do you think?