In 331 BCE, the Persian Empire fell to Alexander of Macedon and became part of the Hellenistic world under the Seleucid Empire. Babylon's significance declined with the establishment of Seleucia on the Tigris as the new Seleucid capital. The Seleucid Empire, at its peak, extended from the Aegean Sea to India, embodying a significant center for Hellenistic culture. This era was marked by the dominance of Greek customs and a political elite of Greek origin, particularly in urban areas.^[44] The Greek elite in the cities was bolstered by immigrants from Greece.^[44] By the mid-2nd century BCE, the Parthians, under Mithridates I of Parthia, had conquered much of the empire's eastern territories.