Media is a region of northwestern Iran, best known as the political and cultural base of the Medes. In 678 BC, Deioces united the Median tribes and made the first Iranian empire, and his grandson Cyaxares united all Iranian tribes to create an even more powerful empire. In 550 BC, Cyrus the Great rebelled against his grandfather, King Astyages, and overthrew the Medians, creating the Persian Empire. Media remained under Persian rule until it was conquered by the Macedonian king Alexander the Great in 330 BC, and it was then granted to the Seleucids, who ruled it until 221 BC, when it was conquered by Parthia. Northern Media became known as Atropatene, now known as Azerbaijan.