Babylon is an ancient city located on the lower Euphrates river in southern Mesopotamia. Babylon functioned as the main cultural and political centre of the Akkadian-speaking region of Babylonia, with its rulers establishing two important empires in antiquity, namely the 18th century BC Old Babylonian Empire and the 7th–6th century BC Neo-Babylonian Empire, and the city would also be used as a regional capital of other empires, such as the Achaemenid Empire. Babylon was one of the most important urban centres of the ancient Near East until its decline during the Hellenistic period.