NATURAL FEATURES
Topography
Alternating bands of high and low terrain extend generally east to west across the country. The four most prominent of these from north to south are the Danubian plateau, the Stara Planina (Old Mountain), or Balkan Mountains, the central Thracian Plain, and the Rodopi (or Rhodope Mountains). The western part of the country, however, consists almost entirely of higher land, and the individual mountain ranges in the east tend to taper into hills and gentle uplands as they approach the Black Sea (see fig. 2).
The Danubian plateau, also called a plain or a tableland, extends from the Yugoslav border to the Black Sea. It encompasses the area between the Danube River, which forms most of the country's northern border, and the Stara Planina to the south. The plateau rises from cliffs along the river, which are typically 300 to 600 feet high, and abuts against the mountains at elevations on the order of 1,200 to 1,500 feet. The region slopes gently but perceptibly from the river southward to the mountains. The western portion is lower and more dissected; in the east it becomes regular but somewhat higher, better resembling a plateau. Bulgarians name local areas within it, but they do not name the region as a whole. It is a fertile area with undulating hills and is the granary of the country.
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.