The northern part of Greece is traversed in its whole length by a range of mountains, the Greek Apennines. This ridge first takes the name of Pindus, where it intersects the northern boundary of Greece, at a point where an ancient route still affords the least difficult passage from Epirus into Thessaly. From Pindus two huge arms stretch towards the eastern sea, and enclose the vale of Thessaly, the largest and richest plain in Greece: on the north the Cambunian hills, after making a bend towards the south, terminate in the loftier heights of Olympus, which are scarcely ever entirely free from snow; the opposite and lower chain of Othrys parting, with its eastern extremity, the Malian from the Pagasæan Gulf, sinks gently towards the coast. A fourth rampart, which runs parallel to Pindus, is formed by the range which includes the celebrated heights of Pelion and Ossa; the first a broad and nearly even ridge, the other towering into a steep conical peak, the neighbour and rival of Olympus, with which, in the songs of the country, it is said to dispute the pre-eminence in the depth and duration of its snows. The mountain barrier with which Thessaly is thus encompassed is broken only at the northeast corner, by a deep and narrow cleft, which parts Ossa from Olympus: the defile so renowned in poetry as the vale, in history as the pass, of Tempe. The imagination of the ancient poets and declaimers delighted to dwell on the natural beauties of this romantic glen, and on the sanctity of the site, from which Apollo had transplanted his laurel to Delphi. From other points of view, the same spot no less forcibly claims the attention of the historian. It is the only pass through which an army can invade Thessaly from the north, without scaling the high and rugged ridges of its northern frontier. The whole glen is something less than five miles long, and opens gradually to the east into a spacious plain, stretching to the shore of the Thermaic Gulf. On each side the rocks rise precipitously from the bed of the Peneus, and in some places only leave room between them for the stream; and the road, which at the narrowest point is cut in the rock, might in the opinion of the ancients be defended by ten men against a host. On the eastern side of the ridge which stretches from Tempe to the Gulf of Pagasæ, a narrow strip of land, called Magnesia, is intercepted between the mountains and the sea, broken by lofty headlands and the beds of torrents, and exposed without a harbour to the fury of the northeast gales.