In Ionia (the modern Aegean coast of Turkey) the Greek cities, which included great centres such as Miletus and Halicarnassus, were unable to maintain their independence and came under the rule of the Persian Empire in the mid-6th century BC. In 499 BC the Greeks rose in the Ionian Revolt, and Athens and some other Greek cities went to their aid. In 490 BC, the Persian Great King, Darius I, having suppressed the Ionian cities, sent a fleet to punish the Greeks. The Persians landed in Attica, but were defeated at the Battle of Marathon by a Greek army led by the Athenian general Miltiades. The burial mound of the Athenian dead can still be seen at Marathon. Ten years later Darius' successor, Xerxes I, sent a much more powerful force by land. After being delayed by the Spartan King Leonidas I at Thermopylae, Xerxes advanced into Attica, where he captured and burned Athens. But the Athenians had evacuated the city by sea, and under Themistocles they defeated the Persian fleet at the Battle of Salamis. A year later, the Greeks, under the Spartan Pausanias, defeated the Persian army at Plataea. The Athenian fleet then turned to chasing the Persians out of the Aegean Sea, and in 478 BC they captured Byzantium. In the course of doing so Athens enrolled all the island states and some mainland allies into an alliance, called the Delian League because its treasury was kept on the sacred island of Delos. The Spartans, although they had taken part in the war, withdrew into isolation after it, allowing Athens to establish unchallenged naval and commercial power.