qnli question: Who found the Archaemenid Empire in 550 BC? sentence: Iran reached the pinnacle of its power during the Achaemenid Empire founded by Cyrus the Great in 550 BC, which at its greatest extent comprised major portions of the ancient world, stretching from parts of the Balkans (Thrace-Macedonia, Bulgaria-Paeonia) and Eastern Europe proper in the west, to the Indus Valley in the east, making it the largest empire the world had yet seen.