Immediately east of the Asopos defile the chain of Œta is at its lowest, barely three thousand feet high, and it is over this part of the range that the modern road is carried. The difficulties of passing it do not, however, decrease in proportion to its height, and no military way or path seems to have been practicable at this point.[109] Farther east the range rises again into peaks of nearly five thousand feet, faced towards the north by the great cliffs which overhang the pass of Thermopylæ. #MT. ŒTA AND THE ASOPOS RAVINE.# Here the Malian Gulf and not the plain forms the foreground of the picture, across which, at a distance of eight or nine miles, a white line can be discerned at the base of the cliffs, the great sulphur deposit of the warm springs. This part of the Œta range was known as Kallidromos. Away beyond Thermopylæ it extends towards the Euripus under the name of Knemis, gradually bending in a more southerly direction down the channel, until it is lost in the distance towards Atalanta. Behind it and above it rises the great grey mass of Parnassus. This very difficult range is rather turned than pierced by the pass of Thermopylæ, the actual passage through the chain being many miles south of the pass itself. There is one point with reference to it which is not always recognized. There was and is a second pass[110] through it leading direct to the Dorian plain by way of the great ravine of the Asopos, a pass, too, of which the Persian army actually made use after Thermopylæ had been won. It would seem strange at first sight that the Persian generals, when they found Thermopylæ so hard to force, did not nullify the defence of it by marching into Doris this way. The defile of the Asopos issues abruptly on to the Malian plain some three and a half to four miles west of the Western Gate of Thermopylæ. Its bottom is merely formed of the stony river bed, at first some fifty yards wide, but rapidly contracting, until a little farther up the chasm it is only twelve feet wide between absolutely sheer cliffs from seven to nine hundred feet high. This winding rift in the mountains continues for some three and a half miles from the entrance, and then suddenly broadens out into a wide upland valley, behind the range of Œta, from which there is a long but not difficult passage to the Dorian plain.[111] This valley was, no doubt, the land of those Œteans whom Thucydides mentions in his account of the circumstances leading to the foundation of Heraklea Trachinia.