The archaeological site of Alos is strategically located between the foothills of Mount Athros and the shores of the Pagasitikos Gulf. According to mythology, the founder of the city was King Athamas. Homer mentions that Alyes took part in the Argonautic campaign.

Two cities were known by the name of Alos and were located in Achaia Fthiotida, as our region was called in antiquity. Alos of classical times, located near the Pagasitikos, was destroyed in 346 BC by the Macedonian general Parmenion, general of Philip II.

The New Alos of Hellenistic times, which was located at a distance of about 2 km from the previous one, was founded around 302 BC by Demetrius Poliorcetes. The city, well laid out, was surrounded by imposing fortified walls, reinforced with towers. In its territory was the largest part of Mount Othris, the plain of Souropi and shared the periphery of Almyrus with the city of the Fthiotis Thebes. Its economy was based on agriculture and animal husbandry. For their trade transactions, the Alies minted their own coinage, on which the myth of the journey to Colchis was depicted. The city was abandoned in 265-260 BC, probably after a devastating earthquake.