From Fennau, is possible to make a small detour and reach the "de S' Edera" cave, 200 meters long (the explored part), where endemic troglobitic species have been found, including the Sardaphaenops supramontanus beetle and the Neobisium sardoum pseudoscorpion.
The cave is located in the Fennau locality, in the municipal territory of Urzulei, and takes its name from the large ivy plant present near the cave entrance. It was first explored in the 1960s and is part of a large karst system of which, to date, only a few caves have been explored and opened to visitors. Its length is about 16 km with a drop of up to minus 256 meters and with the entrance located at an altitude of about 944 meters above sea level.
Inside the cave, developed on different levels of the mountain with galleries and even large rooms in which we find secular concretions, and also three watercourses that join and flow into the Su Gologone spring source, a freshwater spring (in the territory of Oliena, it is the most important spring source in Sardinia) about 22 km away from the cave, and which gives rise to the stream that flows into the Cedrino river.
