Bulgaria provides various habitats for reptiles. The country falls within six terrestrial ecoregions of the Palearctic realm: Balkan mixed forests, Rodope montane mixed forests, Euxine-Colchic deciduous forests, Aegean and Western Turkey sclerophyllous and mixed forests, East European forest steppe, and Pontic-Caspian steppe. Bulgaria has varied topography. From north to south the main geomorphological regions are the Danubian Plain, the Balkan Mountains, the Sub-Balkan valleys, the Rila-Rhodope massif to the south-west, the Upper Thracian Plain and the Strandzha mountains to the south-east. Most of the country is situated within the humid continental climate region, with Alpine climate in the highest mountains and Mediterranean climate in the southernmost regions. The highest diversity of reptiles is recorded in southernmost Bulgaria - the valley of the river Struma, the eastern Rhodope Mountains, the southern reaches of the river Maritsa and Strandzha. Reptiles are also most diverse at low altitudes; 15 species occur below , and only five species are common above .