It consists mainly of metamorphic rocks. Viewed from the north from the Strumeshnica River valley or from the south from the Syrsko Field, Belasitsa rises like an imposing wall. The mountain ridge is narrow, sharp, and in places rocky or covered with pastures. The southern slopes are rocky, steep, and sparsely forested, while the northern slopes are forested, cut through by very deep ravines and rushing rivers and streams with small waterfalls. The northern foothills of the mountain, known as Podgorie, are formed by thick accumulative and accumulative-deluvial strata that retain abundant water reserves. The lateral ridges are short and steep.
The rivers originating in the mountain are short, steep, and turbulent, and flow into the Strumeshnitsa and Struma rivers on the right.
About 1,200 plant species have been recorded in Belasitsa, representing approximately one-third of Bulgaria’s flora. In the Bulgarian section of the mountain, 102 species of high conservation importance have been identified, of which 24 are protected under the Biodiversity Act; 38 species are listed in Bulgaria’s Red Book, and 29 are protected under the Convention on International Trade in Endangered Species of Wild Fauna and Flora.
Belasitsa’s greatest treasure is its broadleaf forests, particularly the domestic chestnut, which thrives exclusively north of the main ridge at elevations of 900–1,000 meters. Southwest of Petrich, covering an area of 1,312 hectares, lies the Kongura Reserve, which preserves natural ecosystems of beech and sweet chestnut.
Belasitsa also provides a refuge for numerous vertebrates—8 species of amphibians, 15 species of reptiles, 120 species of birds, and over 50 species of mammals.
