Pre-Colombian Casas Grande Olla Pot, Arizona, c. 1150-1450 , Zoomorphic Polychrome Decoration. The Casas Olla Pot is made of clay and has a rounded, bulbous shape. It's surface is decorated with geometric patterns using black and red pigments. The pots served practical purposes in daily life in the pre-Columbian cultures of the southwestern US and modern-day northern Mexico. Their size and shape made them suitable for holding liquids, grains and food. The intricacy of the decoration and the care in construction also suggest they were valued items, sometimes used in ritual context or as trade goods.