These mountains separate Barcelona from the Vallès plain and their tallest peak is the Tibidabo, at 512 m. Other main summits are: Turó del Puig, Puig d'Olorda, Turó de Valldaura, Turó de la Magarola, Puig d'Ossa, and Puig Madrona. The valleys of the Llobregat and Besós Rivers, the plain of Barcelona, and the Vallès basin, mark the geographical boundaries of the Collserola massif.