In the meantime Xerxes, with his monstrous land army, was marching on, and the only place where it seemed to the council at the Isthmus that he could be met and stopped was at a place in Thessaly, where the mountains of Œta rose up like a steep wall, leaving no opening but towards the sea, where a narrow road wound round the foot of the cliff, and between it and the sea was a marsh that men and horses could never cross.  The springs that made this bog were hot, so that it was called Thermopylæ, or the Hot Gates.