Valchi Dol (Wolf Gully) is the least known reserve in the Rhodopes, but it is the only one created exclusively for the unique bird population. Its location is beside the Cold Well Dam, and it covers the ridges that surround the homonymous gully. There are mainly oak forests, so it is especially beautiful and colourful here in October, when the mating season of the stags begins, and the forest echoes with the appealing roars of the male animals, sounding like grunts. This is the largest stag stock in the country, so stags can be seen any time at the numerous meadows and open spaces, prevailing in the area. However, the master's part is played by the wolves here – they execute the natural selection process among the hoofed game. But the basic purpose of Wolf Gully is to guard the exceptionally rich bird population, and especially the big birds of prey. There are groups of bald vultures, imperial eagles, black vultures and cross eagles, and they can be observed at any time. The highest peak in the area is St. Ilia, keeping on its top the remains of an ancient Thracian fortress. Many ridges curve down from the peak, providing panoramic views of the dam and the Southern Rhodopes.