The range is about 110 km (68.35 mi) long and 50 km (31.07 mi) wide, the highest peak being Ruen (Руен) at 2251 m, which constitutes the main orthographic knot on the very border between Bulgaria and North Macedonia. The steepest slope is in the west, stretching down from Carev Vrv (Царев Врв; "Tsar's Peak"). It is the northernmost and highest part of the Osogovo-Belasica group and is situated between the Kyustendil and Kamenitsa Valleys, Dobro pole and Bregalnica and Kriva Reka river valleys. The western slopes are steep and the south-eastern ones are slant. The mountain itself is a granite massif of crystal rocks. It has a prominent volcanic relief made of conic peaks and volcanic tuff and is rich in polymetal ores.
