The mountain of Oshtrankuh (4,330 m) in the high central Zagros c.80 km south-west of Borujerd. Gaharl lake, of glacial origin, c.1.75 km long and 600 m wide, lies at 2,350 m in the central valley, with a dense stand of very old Salix trees. Other habitats include some Quercus forest and Pistacia-Amygdalus forest on the lower slopes, several fast-flowing perennial mountain streams, montane steppe, alpine meadows, rocky mountain slopes and high crags. Plants include Daphne angustifolia, Euphorbia species and Circium congestum. Land ownership is public.
See box for key species. The breeding bird fauna is characteristic of the high Zagros and includes some woodland species typical of lower elevations. Other notable species include Dendrocopos medius, Melanocorypha bimaculata, Hirundo rupestris, Ficedula semitorquata, Parus lugubris, Pyrrhocorax graculus, Montifringilla nivalis and Emberiza buchanani. Hippolais icterina was thought to have bred in 1974. At least 81 species have been recorded in the reserve.