Period III lasted from the year 350 to 650 CE and is the so-called classical period of Teotihuacan, during which the city reached the apogee of its influence in Mesoamerica. Its population was estimated at 125,000 inhabitants, or more, and the city was among the largest cities of the ancient world, containing 2,000 buildings within an area of 18 square kilometers. It was also during this high period when Teotihuacan contained approximately half all people in the Valley of Mexico, becoming a kind of primate city of Mesoamerica. This period saw a massive reconstruction of monuments; the Temple of the Feathered Serpent, which dates back to the previous period, was covered with a rich sculptural decoration. Typical artistic artifacts of this period were funeral masks, crafted mainly from green stone and covered with mosaics of turquoise, shell or obsidian. These masks were highly uniform in nature.