The Forno dos Mouros (moors furnace) is a big carved outcrop on the western slope of the Arestal mountain. Located at the altitude of 700 meters, dominating the wide landscape that extends over the hills lower down. The artistic expressions in the region, called Atlantic Art, dates back to the IV Millennium B.C. and coincides with the emergence of the megalithic times; in these old times, the dependence on agriculture and pastoralism dictated a new relationship between man and nature, with the imaginary and the symbolism to be on the basis of the appearance of an abstract art materialized in outdoor boulders. One of the most beautiful and representative examples of Peninsular Atlantic Art in the North of Portugal is, without doubt, the Forno dos Mouros.
The location of Forno dos Mouros is coincident with the geological contact between shale and granite, which could be one of the reasons for the petroglyph made here. The Arestal mountain is now covered in large part by plantations, but the understory shows sometimes a swamp forest dominated by the alder buckthorn, a consequence of the constant humidity that this mountain is subject to being the first barrier to the clouds coming from the Atlantic. Along the streams appears often the common holly, and on clearings do not lack the knapweed, plant confined to the Portuguese territory. The river Bom (good) – that down stream becomes river Mau (bad) – we can observe, at dawn the otter, going by, finding the fish on which they feed. Among the amphibians, the iberian frog with his characteristic dark mask beside the eye can be observed always near the water. In this valley still takes refuge the pedunculate oak woodland that once covered much of the Arestal mountain and housed remarkable species such as the great spotted woodpecker.
