The emergence of Susa as a city, as determined by radiocarbon dating, dates back to early 4,395 BC. There are dozens of prehistoric sites across the Iranian plateau, pointing to the existence of ancient cultures and urban settlements in the 4th millennium BC. During the Bronze Age, Iran was home to several civilizations including Elam, Jiroft, and Zayande River. Elam, the most prominent of these civilizations, developed in the southwest of Iran, alongside those in Mesopotamia. The emergence of writing in Elam was paralleled to Sumer, and the Elamite cuneiform was developed since the 3rd millennium BC.