World's First Superpower: How Huge Was the Persian Empire? The Achaemenid Persian Empire (550-330 BCE), at its zenith under Cyrus the Great and Darius I, was the largest ancient empire, spanning over 5.5 million square kilometers. It stretched from the Indus Valley (modern Pakistan) eastward to the Balkans westward, and from the Black Sea northward to Egypt and Ethiopia southward, encompassing 20 satrapies and up to 44% of the world's population. #PersianEmpire #Persian #AncientHistory #History