The Greek town under Persian siege during the oldest recorded tsunami, in 479 BC, was Potidaea.
The event occurred during the Persian campaign in Greece after the Persian army’s defeat at Plataea. Herodotus describes Persian forces attacking Potidaea, a coastal settlement on the Pallene peninsula, when the sea unexpectedly withdrew. The attackers moved onto the exposed seabed, but a powerful surge returned and drowned many of them.
The account is important because it is one of the earliest written descriptions of tsunami behavior: sudden sea retreat followed by a destructive flood. The event is commonly associated with the 479 BC Potidaea earthquake, although the precise earthquake source remains uncertain.
A common mix-up is with Salamis, Marathon, and Plataea. Those places are strongly linked to the Greco-Persian Wars—Salamis to a naval battle, Marathon to an earlier Greek victory, and Plataea to the land battle of 479 BC—but Potidaea is the town named in the tsunami account.