The border between Bulgaria and Serbia serves as a major transit corridor connecting Central Europe with Turkey and the Middle East. The frontier runs through a hilly, agricultural region that marks the transition between the main Balkan mountain range and the Morava river valley in Serbia. The primary crossing point for virtually all international traffic is at Kalotina on the Bulgarian side and Dimitrovgrad (often referred to by its old name, Caribrod) on the Serbian side. This crossing lies on the main E80 highway, the direct route between the two capital cities, Sofia and Belgrade.
As a result of its strategic importance, this border can become very congested, especially during the summer months when European guest workers are traveling to and from Turkey, and during holiday weekends. There are a handful of other, much smaller crossings in more remote areas, but they are not suitable for major traffic. The region has a complex history, with territories and populations having shifted between the two nations, particularly after the early 20th-century Balkan Wars. Today, the crossing is a modern, if often busy, gateway that is essential to the flow of goods and people in Southeast Europe.