The force of nature can be seen in the Vall de Sau-Collsacabra in the form of a complex relief: scarps of an average of 1,100 metres high, the Sau Reservoir and the damp groves of Les Guilleries make up an area that is ideal for practicing outdoor activities. The heyday of this valley was between the eleventh and thirteenth centuries, as we can see in the Monastery of Sant Pere de Casserres in Les Masies de Roda—a jewel of Romanesque architecture. The Sau Reservoir, at Vilanova de Sau, is a water sports paradise. Nearby, Tavertet and the scarps bear witness to 5,000 years of history. Rupit has preserved its attractive medieval style, and Sant Joan de Fàbregues is an example of primitive Romanesque built in the middle of the escarpment and offering magnificent views.