The Natural Park Arribes del Duero is a deep gorge along the River Duero. It stretches for eighty kilometres, of which fifty run alongside the Portuguese border. There are a number of hydroelectricity dams. The sides of the cliffs, where vultures, eagles and black storks breed, are over 200 metres high in places. On gentler cliffs are terraces of olive trees and vines. Boat trips can be arranged.