When the Greeks studded the west coast of Asia Minor and the adjacent islands with migration settlements in the eleventh and tenth centuries B.C. they placed themselves in permanent contact with a world – that of Anatolia – which was Aegean on the fringes but was to appear increasingly alien in its environment when in due course they penetrated eastward. The heart of Anatolia between 30° and 36° East is formed by a plateau with a general level of 750–1,050 metres above the sea, which is enclosed within a framework of high mountain ranges. It has a sump in the centre south of Ankara which is filled by a salt lake (the ancient Tatta); and it has numerous small endorrhoean basins in the lake district of Pisidia in the south-west, with the result that west of the Cilician plain the south coast has no allogenic rivers. But elsewhere the mountain crust is broken by big rivers draining outwards, and the plateau is consequently less arid and more convenient to traverse than the Iranian one further east. There are some considerable mountain ranges and peaks on the plateau itself; but the valleys are generally shallow and open, and despite the desolate areas of the Tatta Lake and (further west) the arid Axylus where not even thistles would grow, the country as a whole forms a habitational unity. The big rivers tend to take a westerly course because of the tilting of the plateau. But they are turned back when they begin to breach the mountain barrier; and they then force their way through a series of deep gorges before entering the flat-bottomed valleys which lead them to their damp coastal plains.