In the western section of the Serra do Alvão, that includes the imposing mountainous massif that incorporates the Serra do Marão, the River Olo runs through this protected area, between cranks and rocky outcrops and cuts across the rocks of the Fisgas de Ermelo, falling in cascades around 250 m high. This area is one of the most beautiful zones of the region, due to the impressive force of its waters and is represented within the Park' s symbol.

The course of the river Olo joins together two distinct realities. At an average altitude of 1000 m, in the zone of Lamas de Olo, granite stone and mountainous vegetation predominates; whereas down below, in Ermelo, where the altitude is around 450 m, slate and green landscapes such as in the Minho region predominate.

Slate, granite and straw are the main materials used in order to build the houses of the characteristic villages in Lamas de Olo, Anta or Ermelo, where time moves so slowly that we seem to be far from urban life, even though Oporto is only a one-hour journey away. In order to gain a better idea of the lifestyle of the people living in these locations, visit the eco-museum in Arnal, that recreates the environment of a traditional village in the Serra do Alvão.