The urban section of the Reserve (within GRA, Grande Raccordo Anulare) is characterized by the several bends of the river Aniene, while the out-of-town stretch - not yet belonging to the Reserve - is dominated by the morphology of the Roman countryside, with elements of great interest like the springs of "Acqua Vergine", the crater of the ancient Castiglione Lake, and the area of Pantano Borghese. The land is flat and over the years this feature has favored the evolution of oak woods (with Common oak, Turkey oak, Downy Oak, and Italian oak), together with Elm, White Willow, Ash tree, and Maple favored by the presence of the river. As far as wildlife is concerned, we should mention the presence of the freshwater crayfish and crab, which usually live in clean waters: for this reason, they represent two important ecological indicators. Some bat colonies also live in the area. Inside the Reserve, Pratone delle Valli is of particular naturalistic interest, as well as Cervelletta district. Another important monument is Ponte Nomentano, a bridge probably dating back to the period of Menenio Agrippa: its medieval and Renaissance superstructures have been painted thousands of times by several artists over the centuries.