From the high, snowcapped slopes of the Cordillera Real and the Apolobamba range, the descent to the eastern plains is extremely precipitous, plunging through a rainy and heavily forested belt of rugged terrain known as the Aymara word roughly translated as “Warm Lands” or “Warm Valleys.” The Yungas form the southern end of a region that extends along the eastern Andes of Colombia, Ecuador, and Peru (where it is called the Alto Selva [“High Rainforest”]) and continues southeast through Bolivia as far as Santa Cruz.In Bolivia the name Yungas often refers to a smaller region northeast of La Paz, which, like the neighbouring region of Alto Beni (the upper basin of the Beni River north of Caranavi), is part of the larger Yungas region.The margins of the Altiplano are characterized by numerous spurs and interlocking alluvial fans (accumulations of silt, gravel, and other debris that were brought down from the mountains and that have spread out in the shape of a fan).In the middle of the Altiplano are the Titicaca and Poopó lakes and basins, which traditionally have been important agricultural, economic, and cultural areas.
To the north of the Cordillera Real is the Apolobamba range, bordered on the western slopes by lakes and protected areas where vicuñas, alpacas, and llamas thrive.
Terraced fields built hundreds of years ago lie at the foothills of snow-covered peaks, which have been sacred to the Indians since ancient times.
The surface of the Altiplano is composed mostly of water- and wind-borne deposits from the bordering mountains, and it slopes gently southward, its evenness broken by occasional hills and ridges.
In southern Bolivia the Andes become much wider and are formed by a high, tilted block called the Puna, with west-facing escarpments and more gentle eastward slopes down to the plains.
The Puna is broken up by the Valles, a system of fertile valleys and mountain basins that are generally larger and less confined than those in the Yungas.