[2] The reserve is situated a few kilometres to the north of the town of Karlovo in the northern section of Plovdiv Province.

[1][3] The altitude of the reserve varies between 1000 and 2169 m. The southern slopes of the Balkan Mountains have a milder climate with a snow cover lasting for an average of 120 days annually.

45 species are listed in the Red Book of Bulgaria, of them 20 are endemic to the country, such as Primula frondosa, Centaurea kerneriana, Campanula trojanensis, Stachys alpina, etc.

[1][3] Stara Reka Reserve contains the westernmost population of chamois along the southern slopes of the Balkan Mountains.

It is also an important sanctuary for the brown bear, gray wolf, wildcat, European pine marten and Eurasian otter.