Vlahina is situated between the valley of the river
Struma to the east that separate it from the mountain ranges of
Rila and
Pirin in Bulgaria, and the valley of the river
Bregalnica to the west that separate it from Golak and
Plačkovica in North Macedonia. To the northwest, entirely in Bulgarian territory, the valley of the
Eleshnitsa, a right tributary of the Struma, and the Chernata Skala Saddle (930 m) form the connection with
Osogovo, to the north the Skrino Gorge along the Struma separates it from
Konyavska Planina, to the south the valley of the Sushichka reka and the Sedloto Saddle (1,619 m) link it to
Maleshevo Mountain. Its northernmost part between the Eleshnitsa and the Struma is known as the Ruen Mountain. Within these boundaries Vlahina reaches a length of about 50 km in direction north–south, and the width varies between 12 km to the north and 30 km to the south. The northern part of the main ridge is in Bulgaria; the middle and southern section forms the Bulgaria–North Macedonia border. The ridge is generally flat, with gentler eastern slopes and steeper western ones. The highest summit is Ogreyak (1,924 m), which rises in the southernmost part of Vlahina near the Sedloto Saddle. It is built up mainly of cracked metamorphic rocks —
gneiss and
amphibolites — but also of
diorite, granite gneiss,
limestone,
marl and others. North of the Bulgarian village of
Brestovo is the little known rock formation
Komatinski Rocks. The climate is transitional continental and
alpine. The eastern slopes are drained by right tributaries of the Struma, such as Kopriven, Logodashka reka, Stara reka and others, while the western ones are drained by several left tributaries of the Bregalnica. The predominant soils are cinnamon forest soils. Most of the slopes up to 700–800 m are covered with deciduous forests of
oaks,
ashes,
maples and
hornbeams, as well as
xerophyte bushes and grass associations. The higher areas are forested with
beeches. == Settlements and transport ==