The superb syenitic and porphyritic mountain group of Vitosh forms the eastern bastion of the Mœsian plateau. Immediately to the east of it the deep valley of the Isker pierces the whole of the Balkan Mountains, and, crossing the plain of Sofia, takes its course in the direction of the Danube. The upper valley of this river and the plain mentioned form the true geographical centre of European Turkey. From Sofia diverge some of the most important roads of the peninsula, one leading through the valley of the Isker to the Lower Danube, another along the Morava valley into Servia, a third by way of the Maritza into Thracia, and a fourth down the Struma into Macedonia. It is said that Constantine the Great, struck by these important natural advantages of Sofia, then called Sardica, thought of making it the capital of his empire. {133} [Illustration: TIRNOVA.] The Turks apply the name of Balkans to all the mountain ranges of the peninsula, but geographers restrict that term to the Hæmus of the ancients. This mountain rampart begins to the east of the basin of Sofia. It does not form a regular chain, but rather an elevated terrace sloping down gently in the direction of the Danube, whilst towards the south it presents an abrupt slope, it appearing almost as if the plateau on that side had suddenly sunk to a lower level. The Balkan consequently presents the appearance of a chain only when looked at from the south. But its contours even there are only slightly undulating; there are neither abrupt projections nor rocky pyramids, and the prevailing character is that of long-stretched mountain ridges. The porphyritic mountain group of Chatal, which rises to the south of the principal chain, constitutes the only exception to this gentleness of contour. Though inferior in height to the summits of the Balkan, its steep precipices, slashed crests, and chaotic rock masses strike the beholder, and the contrast between this mass of erupted rock and the gentle slopes of the calcareous hills which surround it is very great. The uniformity of the northern slopes of the Balkan is such that, in many places, a traveller is able to reach the crest without having come in sight of mountains. When the woods have disappeared from the Balkan, these undulating slopes will be deprived of their greatest charm; but, as long as the forests ornament them as now, the country will remain one of the most delightful in Turkey. Running streams flow through each valley, bordered by pastures as brilliantly green as are those of the Alps; the villages are built in the shade of beech-trees and oaks; and nature everywhere wears a smiling aspect. But the plains which extend to the Danube are barren, and sometimes not a single tree is visible. The inhabitants, deprived of wood, are dependent upon cow-dung dried in the sun for their fuel, and they dig for themselves holes in the ground, where they seek protection from the cold of winter.