The Paiva Gorge is a segment of the Paiva River where the bed narrows and extends from Alvarenga Bridge (G36) to Vau (G30). This bridge, dating from the eighteenth century, was built by the bishop of Lamego (D. João) and was completed in 1791, by decree of D. Maria I. It is composed of three arches whose main is 7 meters from height. On this bridge we can observe the sinuous encasement of Rio Paiva and the incision of the valley that surrounds it. This strangulation is due to greater resistance of Alvarenga granite to weathering and erosion, compared to other surrounding rocks. In fact, on the section that is designated as the “gorge”, the Rio Paiva traverses the Alvarenga granite, narrow outcrop, which, by presenting a greater hardness than the surrounding rocks, namely schist, makes the river erosion more difficult, giving a narrower and stiffer bed. This geological phenomenon is called differential erosion. In this sector there are also giant pots and the superb Aguieiras waterfall. This portion of the Paiva River is also a classic of the white water of Portugal, whose difficulty of rapids is classified IV + and V on a scale which goes from I to VI. The “Grand Rapide” deserves special attention (class IV + / V on a scale from I to VI), a fast and technical technique, which is the scene of the spectacular Kayak Extremo event of the Paiva Fest which takes place every year around the holiday of 25 April.