 The entrance to the Trachinian plain was only half a plethrum [] in breadth, but the surface of the plain was 22,000 plethra [], according to Herodotus.The same writer states that the city Trachis was 5 stadia from the river Melas, and that the river Asopus issued from a gorge in the mountains, to the south of Trachis.According to Thucydides, Trachis was 40 stadia from Thermopylae and 20 from the sea.