Among the once glaciated Mediterranean mountains Orjen was outstanding for one of the biggest ice cap in the region. A 150 km² covered 1/3 of the area. All part above 900 m were buried under a thick sheet of ice from where several glacial tongues descended to 500 m above sea level. Traces of glacial activity are evident in any part of Orjen as in the Bijela gora plateaux. No glacial lakes survive today as they were extinguished due to the porosity of the karstified landscape.