The southern edge of the Danubian plateau blends into the foothills of the Stara Planina, the Bulgarian extension of the Carpathian Mountains. The Carpathians resemble a reversed S as they run eastward from Czechoslovakia across the northern portion of Romania, swinging southward to the middle of that country, where they run westward and cross Romania as the Transylvanian Alps. At a famous gorge of the Danube River known as the Iron Gate, which forms part of the Romania-Yugoslavia border, the Carpathians again sweep eastward, becoming Bulgaria's Stara Planina range. Considered in its local context, the Stara Planina originates at the Timok Valley in Yugoslavia, continues southeastward as it becomes the northern boundary of the Sofia Basin, and then turns more directly eastward to terminate at Cape Emine on the Black Sea. It is some 370 miles in length, and some twelve to thirty miles in width. It retains its height well into the central part of the country, where Botev Peak, its highest point, rises to about 7,800 feet. The range is still apparent until its rocky cliffs fall into the Black Sea. Over most of its length, its ridge is the divide between drainage to the Danube River and to the Aegean Sea. In the east small areas drain directly to the Black Sea. Sometimes considered a part of the foothills of the Stara Planina, but separated from the main range by a long geological trench that contains the Valley of Roses, is the Sredna Gora (Middle Forest). The Sredna Gora is a ridge running almost precisely east to west, about 100 miles long. Its elevations run to only a little more than 5,000 feet, but it is narrow and achieves an impression of greater height. The southern slopes of the Stara Planina and the Sredna Gora give way to the Thracian Plain. The plain is roughly triangular in shape, originating at a point east of the mountains that ring the Sofia Basin and broadening as it proceeds eastward to the Black Sea. It encompasses the Maritsa River basin and the lowlands that extend from it to the Black Sea. As is the case with the Danubian plateau, a great deal of this area is not a plain in strict terms. Most of its terrain is moderate enough to allow cultivation, but there are variations greater than those of a typical plain. [Illustration: _Figure 2. Topography of Bulgaria_]