The Persian Empire began as a collection of semi-nomadic tribes who farmed in the Iranian plateau. Cyrus the Great - the leader of one of these tribes - began to defeat the neighboring kingdoms, including Media, Lydia and Babylon, and united them under one rule. He established the first Iranian empire, also known as the Achaemenid Empire, in 550 BC. The first Iranian empire under the leadership of Cyrus the Great soon became the world's first superpower. It united three important sites of early human civilization in the ancient world under one state: Mesopotamia, the Nile Valley of Egypt, and the Indus Valley of India. Cyrus the Great is immortalized in the Cyrus Cylinder, a clay cylinder .written in 539 BC. With the story of how Babylon was conquered from King Nabonidus and ended the Neo-Babylonian Empire. The Bistun Inscription, a multilingual relief carved on Bistun Mountain in western Iran, extols his virtues and was an important key to deciphering cuneiform. Its impact has been compared to that of the Rosetta Stone, the tablet that enabled researchers to decipher Egyptian hieroglyphics.