From Gouveia, an itinerary crosses the massif via the upper Zêzere Valley. Up on the high rocky plateaux, note the granite boulders sculpted by erosion, such as the Cabeça do Velho ("Old Man's Head"). The source of the Mondego, Portugal's longest river, is indicated at an altitude of 1 360m. Then comes the steep descent via hairpin bends down the upper Zêzere Valley; there, a viewpoint offers a fine view along the length of the upper reaches of the valley presided over by the village of Manteigas.