174. Such was the expedition to Thessaly, which took place when the king was about to cross over from Asia to Europe and was already at Abydos. So the Thessalians, being stripped of allies, upon this took the side of the Medes with a good will and no longer half-heartedly, so that in the course of events they proved very serviceable to the king. 175. When the Hellenes had returned to the Isthmus, they deliberated, having regard to that which had been said by Alexander, where and in what regions they should set the war on foot: and the opinion which prevailed was to guard the pass at Thermopylai; for it was seen to be narrower than that leading into Thessaly, and at the same time it was single, 166 and nearer also to their own land; and as for the path by means of which were taken those of the Hellenes who were taken by the enemy at Thermopylai, they did not even know of its existence until they were informed by the people of Trachis after they had come to Thermopylai. This pass then they resolved to guard, and not permit the Barbarian to go by into Hellas; and they resolved that the fleet should sail to Artemision in the territory of Histiaia: for these points are near to one another, so that each division of their forces could have information of what was happening to the other. And the places are so situated as I shall describe. 176. As to Artemision first, coming out of the Thracian Sea the space is contracted from great width to that narrow channel which lies between the island of Skiathos and the mainland of Magnesia; and after the strait there follows at once in Euboea the sea-beach called Artemision, upon which there is a temple of Artemis. Then secondly the passage into Hellas by Trechis is, where it is narrowest, but fifty feet wide: it is not here however that the narrowest part of this whole region lies, but in front of Thermopylai and also behind it, consisting of a single wheel-track only 167 both by Alpenoi, which lies behind Thermopylai and again by the river Phoinix near the town of Anthela there is no space but a single wheel-track only: and on the West of Thermopylai there is a mountain which is impassable and precipitous, rising up to a great height and extending towards the range of Oite, while on the East of the road the sea with swampy pools succeeds at once. In this passage there are hot springs, which the natives of the place call the "Pots," 168 and an altar of Heracles is set up near them. Moreover a wall had once been built at this pass, and in old times there was a gate set in it; which wall was built by the Phokians, who were struck with fear because the Thessalians had come from the land of the Thesprotians to settle in the Aiolian land, the same which they now possess. Since then the Thessalians, as they supposed, were attempting to subdue them, the Phokians guarded themselves against this beforehand; and at that time they let the water of the hot springs run over the passage, that the