The valleys of the Llobregat and Besós Rivers, the plain of Barcelona, and the Vallès basin, mark the geographical boundaries of the Collserola massif.

In the park, over a thousand major plants and around thirty plant communities have been catalogued; including forests of Aleppo pines and nut pines, evergreen oaklands, riverside copses, maquis and scrublands, brush, and savannah grasslands.

This diversity allows for the existence of a rich, varied wildlife; including wild boar, fox, genet, stone marten, badger, rabbit, and squirrel; blue tits, whitethroats, treecreepers, woodpeckers, bee eaters, doves, goshawks, sparrowhawk, and rat-catching eagles; salamanders, newts, green tree frog, the small southern frog, toads, the small spotted toad, the Mediterranean turtle, the giant turtle, the ocellated lizard, snakes, and so on.

The Collserola Park is used extensively by the inhabitants of Barcelona and the other towns that border it.

A path that follows the ridge of the Serra, known as the "Carretera de les Aigües" (Water Road), has been extensively improved for cyclists.