The first king of the Persian Empire was Cyrus, who issued the famous decree for the Jews to return to their homeland to rebuild their Temple.
The Persian Empire was founded by Cyrus in 536 BC., after they succeeded the Babylonian Empire.
This map reveals the Persian Empire in 580 BC under its greatest ruler Darius I. The Persian Empire Map of the Achaemenid Persian Empire at its Greatest Extant (490 BC.)