83% of the Rhodope Mounatins are in Bulgaria, the remainder are in Greece. They are one of the most biodiverse areas in the whole of Europe. The river Mesta crossing the Rhodopes (wikipedia)
The Rhodope (Rodopi) Mountains boast the richest and most varied fauna of all the Bulgarian mountains. Indeed they are probably the most important region in Europe in terms of their biodiversity. This is not simply due to the vast area of the Rhodope (Rodopi) Mountains, but also because of the great variety of terrain, vegetation and climate. Brown bear (Ursus arctos), wolf (Canis lupus) and wild cat (Felis silvestris) all survive here in significant numbers, as do more species of bat than anywhere else in Europe. There are also many interesting birds, particularly raptors. Indeed the Rhodope (Rodopi) Mountains are the most important place in Europe for birds of prey with 36 species having been recorded here. In particular, the Rhodope (Rodopi) Mountains are renowned by birdwatchers from around the world for elusive species such as wallcreeper (Tichodroma muraria), griffon vulture (Gyps fulvus), black vulture (Aegypius monachus), Egyptian vulture (Neophron percnopterus) and masked shrike (Lanius nubicus).
This is one of the top locations in Europe in terms of its biodiversity. Here are some statistics about the region: Some 1900 species of higher plant including many local, Bulgarian and Balkan endemics; about 300 species of birds including 36 species of birds of prey; some 70 species of mammal including good stable populations of brown bear and wolf, and at least 27 species of bat! As for invertebrates, the Rhodope (Rodopi) are one of the richest regions in Europe for butterflies, moths, dragonflies and many other types of bugs and beetles.
The region is particularly notable for the Karst areas with their deep river gorges, large caves and specific sculptured forms, such as the Trigrad Gorge. Fifteen reserves have been established in the region, some of which under UNESCO protection. The mountains are famous for the largest coniferous woods in the Balkans, their mild relief and the lush vegetation in the western parts as well as the abundance of birds of prey in the eastern areas.