[1] The main section consists of the steep slopes of an escarpment dropping sharply more than 1,000 metres (3,300 ft) in elevation from a dissected plateau to the Zaña River.

The semi-tropical forests in this section, found at elevations above 2,000 metres (6,600 ft), are the distinguishing feature of the Refuge.

The forests are found between the desert coasts of western Peru and the rainforests of the Amazon Basin to the east.

The Peruvian government recognized the uniqueness of the forests in 2010 by creating the "Reserved Zone of Udima" consisting of 30,503 hectares (75,370 acres) of land.

[3] The Zaña River valley, overlooked by the Refuge, contains many pre-Columbian archaeological sites, including the oldest known irrigation canals in the Americas.