Simanya cave or Great Simanya cave is a cave in the Sant Llorenç del Munt massif located in the municipality of Sant Llorenç Savall, in Vallès Occidental. It has a route of 372 m and a gradient of 8 m. The entrance is 885 m in height. It is in the Llor canal on the eastern side of Montcau and at a distance of almost 400 m from the summit. It is a hypogean talveg of karst origin formed by conglomerate.