South from the Kyustendil Hollow the massif is divided in two parts by the Struma River – the Eastern Part – Rilo-Rhodope Massif, and Western Part – Macedono-Serbian Massif. The highest mountain and peak of the whole Macedono-Rhodope Massif and on the Balkans is Mount Musala (2925, 4m) in Rila Mountains (Bulgaria). The Bulgarian part of the Rilo-Rhodope Massif includes the mountain ranges of Rila Mountains, Pirin Mountains, Rhodope Mountains, Slavyanka Mountains, Sturgach Mountains.