Babylon fell in 539 BC when it was conquered by the Persian Empire led by Cyrus the Great. This event marked the end of the Neo-Babylonian Empire. There are varying historical accounts about how the city fell—some sources say it was taken without a battle, while others describe a siege involving a surprise attack during a festival. Nabonidus, the last Babylonian king, surrendered and was exiled, and Belshazzar, who was left in charge, may have been killed during the invasion. The fall of Babylon was a significant moment in ancient history, ending Babylon's political independence but allowing it to continue as a cultural and religious center under Persian rule.