The river Trešnjica springs on the southwest side of Povlen at a height of 1185 m, and flows into the Drina near Gornja Trešnjica at a height of 180 m. The distinctly gorge valley of Trešnjica is partly canyon-like in appearance. In the middle course, it flows through a picturesque canyon close to 6 km long, which is cut in an 800-1000 m high area. In the Trešnjica canyon, it receives the largest right tributaries - Sušica and Tribuća.
Tribuća is the richest tributary of Trešnjica, it is 7 km long and springs below Tornička Bobija. With its lower course, it separates the Boškovac plateau from the Gornja Košljanska surface, building an almost impassable gorge attractive for mountaineers. The Trešnjica canyon is a natural asset of exceptional importance that has been placed under protection in order to preserve the habitat of the population of the natural rarity of the griffon vulture, geomorphological forms with the river and valuable heritage. One of the most beautiful is the habitat for 17 pairs of griffon vultures, which is the only one still living in the Uvac canyon. They represent an endangered species that is threatened with extinction and environmentalists are doing everything to save them from extinction.
Rich in natural beauties and rarities, the settlement of Gornja Trešnjica is also the founder of education in this area with a primary school from 1836. A trout pond and a number of mills were also built. The environment is rich in medicinal herbs and fruits, so this ecologically clean zone should be used for healthy recovery and rest. Specific for the Trešnjica canyon is that every spring, young fish, the "queen" of the Drina, emerge from the Drina to the natural spawning ground.
A full-system California trout pond was built on the Trešnjica River. The application of modern technology, which is based on the injection of liquid oxygen into the water, is unique in Serbia, which has tripled the annual production.
The Trešnjica canyon is a natural asset of exceptional importance, which has been placed under protection, in order to preserve the habitat of the population of the natural rarity of the griffon vulture. It is one of the most beautiful canyons and represents a habitat for 17 pairs of griffon vultures, which is still the only one inhabited in the Uvac canyon. It is the largest bird of prey in this area and feeds exclusively on the remains of dead animals, so due to its exceptional sanitary role, we call it "the Emperor of Heights and the Cleaner of Nature".
The griffon vulture is an endangered species that is threatened with extinction and environmentalists are doing everything to save them from extinction. The female lays only one egg during the year and for that reason it is extremely difficult to protect them and keep them from disappearing. Specific to the Trešnjica canyon is that every spring, young fish, the "queen of the Drina", emerge from the Drina to the natural spawning ground.