But the greatest river and most important landmark of the interior is the Halys, which describes a broad circuit through the heart of the plateau, enclosing towards the north-east a tract about a hundred and fifty miles across which mostly lies in the basin of the river, well watered by its many tributaries. This region is one of the most important in our subject. Though not extensively cultivated, for the stable population even here is relatively small, it is none the less highly fertile. Its hills and slopes are mostly green with pastures, and in the flat valleys are long reaches suitable for the plough. Another favoured district lies southward from the Halys, passing by Mount Argæus, skirting the eastern edges of the plain, and watered by streamlets from the Anti-Taurus. Here in the vicinity of Tyana are wide acres of corn-land, gardens are plentiful, and even trees abound. [Illustration: PLATE VIII WOODLAND ON THE SOUTH SLOPES OF TAURUS (_See pp. 19, 47._)] Woodland is rare in the interior, but highland trees grow in profusion on the mountain-sides. The middle heights of the Taurus are covered with virgin forest, especially on the southern aspect, where every variety of European tree is found; and the pine-woods of Phrygia in the west have been a feature of the country throughout its history.[21] The slopes overlooking the Black Sea, however, catch the chief share of the northern rains, and here consequently forest-land is plentiful,[22] and nearly continuous along the coast. The interior is almost rainless in the summer-time,[23] and relies chiefly for its water supply on the winter storms, and later melting of the mountain snows. Owing to its high elevation above the sea the cold season is severe and persistent: the bleak winds from southern Russia sweep across its plains and open spaces, driving the population of the exposed areas for shelter into houses either sunk below the surface of the ground or hollowed in the banks of streams. The compensation for this inclement season is ample in the summer weather, when the warm sun shining down from blue skies is tempered by refreshing breezes which the altitude produces—features of climate that distinguish this tableland from the southern coasts, and from the plains of Syria.