The ancient civilization around Susa was known as Elam, which was an ancient pre-Iranic civilization located in what is now southwestern Iran. It is believed to have been founded around the mid-3rd millennium BC and lasted until the arrival of the Iranian tribes in the area in the first half of the 1st millennium BC. Elam was centered in the far west and the southwest of modern-day Iran, stretching from the lowlands of what is now Khuzestan and Ilam Province as well as a small part of southern Iraq. The ancient Elamite period is considered to be one of the most important and influential civilizations in the region.