Cyrus founded the empire by conquering the Median kingdom, bringing together two powerful ancient peoples: the Medes and the Persians. The Achaemenid homeland was in the province of Fars (Persia) in modern Iran. It was here that rulers built capital cities at Pasargadae and Persepolis. Cyrus continued conquering new territory until his death in 530 BC, defeating King Croesus of Lydia, in modern Turkey, in 546 BC and capturing Babylon in modern Iraq in 539 BC. After this the whole of the former Babylonian Empire, stretching as far as the Mediterranean, fell into Persian hands.

Cyrus died in 530 BC during a campaign to gain territory in Central Asia, having managed to establish a series of forts on the left bank of the River Jaxartes. This came to be regarded as the northern border of the empire. He was buried at Pasargadae in a freestanding stone tomb he had built there.