Peru’s total land area is 1.29 million square kilometers, or about three times the size of California. Peru’s narrow strip of arid desert coast runs 2,400 kilometers between the borders of Ecuador and Chile. Some 50 rivers cascade from the Andes to the coast, though only about a third of these carry water year-round. In these areas, people are entirely dependent on the seasonal rains in the Andes. In Peru’s extreme south, the coast forms part of the Atacama Desert, one of the driest places on earth.
The Andes rise so abruptly from the coast that they can be seen from the ocean on a clear day. They represent the highest mountain chain on earth next to the Himalaya, and Huascarán, Peru’s highest peak at 6,768 meters, is the world’s highest tropical mountain. The Andes are divided into different ranges (called cordilleras in Spanish), which often run parallel to each other. In northern Peru, for instance, the Andes rise four separate times to form different cordilleras known as the Negra, Blanca, Central, and Oriental.
Between these mountain ranges lie fertile inter-Andean valleys and grasslands between 2,300 and 4,000 meters—the so-called breadbasket of Peru, where the majority of its indigenous highlanders live and produce about half the country’s food supply. The Inca and other cultures terraced and irrigated this landscape to grow a range of crops, including maize, hardy grains such as kiwicha and quinoa, and indigenous tubers such as potatoes, olluco, and oca.
On the journey between Cusco  and Lake Titicaca , travelers can appreciate the most extreme of Peru’s mountain climates, the puna or altiplano. These rolling grasslands between 4,000 and 4,800 meters look bleak but form rich pasturelands for Peru’s variety of camelids, including the wild guanacos, the domesticated llamas and alpacas and the highly prized vicuñas. These animals continue to provide wool, meat, and transport for Andean highlanders.
On the eastern side of Peru, the Andes mountains peter out into a series of ecosystems that cascade into the Amazon basin . Near the top of the eastern edge of the Andes is the montane cloud forest, a mist-drenched, inhospitable place that is one of Peru’s most biodiverse habitats. Here live 90 varieties of hummingbirds and over 2,000 types of orchids and butterflies. Clear mountain streams cascade down these slopes, eventually merging to form the broad, muddy, and winding rivers of the lowland rainforest. This carpet of green is the largest jungle on the planet, making up almost 60 percent of Peru’s territory, and stretches thousands of kilometers through present-day Brazil to the Atlantic Ocean.