Elam, a pre-Iranian civilization, was centered in what is now modern-day Iran and southern Iraq. It stretched from the lowlands of Caza Stan and Ilam province to a small part of southern Iraq. The name Elam comes from the Sumerian transliteration Elam, as well as the later Akkadian Elam. Elamites were prominent political forces in the ancient Near East and were also known as Susiana, which derived from its capital Susa. Elam played a crucial role during the Persian Achaemenid dynasty. The Elamite language was unrelated to Persian and other Iranian languages and is considered a language isolate. Elam was primarily centered in modern Kazakhstan and Ilam, with Susa becoming its center from the mid-2nd millennium BC. There are disagreements over the exact location of Elam and Susiana. Elam's history is largely based on Mesopotamian, Sumerian, Akkadian, Assyrian, and Babylonian sources. It is divided into three periods: proto-Elamite, Old Elamite, and Neo-Elamite. Proto-Elamite civilization emerged in the east of the Tigris and Euphrates alluvial plains, combining lowlands and highland areas. Elam was formed as a response to Sumerian invasion during the Old Elamite period. The Elamites were able to hold different regions together under a coordinated government, primarily through a federated structure. The city of Susa, founded around 4000 BC, played a significant role in the cultural formation of proto-Elamite civilization.