How do the Balkan Mountains extend across Bulgaria?

The Balkan Mountains serve as the primary mountain range of Bulgaria and represent an extension of the Alpine-Carpathian folds.1

The range spans approximately 330 miles (530 km) across the country, beginning at the Timok River valley near the border with Serbia. From this western origin, the mountains spread eastward, eventually breaking off abruptly at Cape Emine on the Black Sea. Throughout their course, the mountains widen into several spurs and reach their highest elevation of 7,795 feet (2,376 m) at Botev peak.1

Geographically, the range acts as a major divide between the Danube River to the north and the Maritsa River to the south. While they are no longer a significant barrier to movement, they function as a climatic divide, separating the continental climate of the Danube valley from the transitional climate found to the south. The range is traversed by approximately 20 mountain passes, including the notable Shipka Pass, as well as the Iskŭr River.1