The Andes mountains form the most populated region of Colombia and contain the majority of the country's urban centres. They were also the location of the most significant pre-Columbian indigenous settlement. Beyond the Colombian Massif in the south-western departments of Cauca and Nariño, the Colombian Andes divide into three branches known as "cordilleras" (from the Spanish for Mountain Range). The climate and vegetation of the region vary considerably according to altitude, but as a general rule the land can be divided into the tierra caliente (hot land) of river valleys and basins below 1,000 m; the more temperate conditions of the tierra templada (temperate land) and tierra fría (cold land), which include the most productive land and the majority of the population; and the alpine conditions of the zona forestada (forested zone), páramos and tierra helada (frozen land).