How does the Balkan Mountains range divide Bulgaria?

The Balkan Mountains serve as a major geographic and climatic divide in Bulgaria, splitting the country into distinct regions.12

The range functions as a primary divide between the Danube River valley to the north and the Maritsa River basin to the south. Physiographically, this creates a structural separation between North Bulgaria—which encompasses the Danubian Plain and the Balkan Mountains themselves—and the regions of South Bulgaria, which include the Rila-Rhodope Massif.12

Beyond its physical topography, the range acts as a significant climatic barrier. It separates the continental climate characteristic of the northern Danube River valley from the transitional continental climate found in the southern parts of the country. While the mountains were historically a barrier to movement, they are now crossed by several railway lines and approximately 20 passes, such as the Shipka Pass.1