Please answer a question about the following article about Greece:

By 500 BC, the Persian Empire controlled the Greek city states in Asia Minor and had made territorial gains in the Balkans and Eastern Europe proper as well. Attempts by some of the Greek city-states of Asia Minor to overthrow Persian rule failed, and Persia invaded the states of mainland Greece in 492 BC, but was forced to withdraw after a defeat at the Battle of Marathon in 490 BC. A second invasion by the Persians followed in 480 BC. Despite a heroic resistance at Thermopylae by Spartans and other Greeks led by King Leonidas, and a simultaneous naval engagement at Artemisium,[page needed] Persian forces occupied Athens, which had been evacuated in time, as well as briefly overrunning half of Greece. Following decisive Greek victories in 480 and 479 BC at Salamis, Plataea, and Mycale, the Persians were forced to withdraw for a second time, marking their eventual withdrawal from all of their European territories. Led by Athens and Sparta, the Greek victories in the Greco-Persian Wars are considered a pivotal moment in world history, as the 50 years of peace that followed are known as Golden Age of Athens, the seminal period of ancient Greece that laid many of the foundations of Western civilization.

In 500 BC, Greece was ruled over by who?
Persian Empire