Andean natural region
The Andes mountains form the most populated region of Colombia and contain the majority of the country's urban centers. They were also the location of the most significant pre-Columbian indigenous settlements. 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 West Andes run adjacent to the Pacific coast and is home to the city of Cali. The Central Andes run up the center of the country between the Cauca and Magdalena river valleys (to the west and east respectively) and includes the cities of Medellín, Manizales and Pereira. The East Andes extend northeast towards the Guajira Peninsula, and includes the cities of Bogotá, Bucaramanga and Cúcuta.
Andes
The rough terrain has historically put the costs of building highways and railroads that cross the Andes out of reach of most neighboring countries, even with modern civil engineering practices. For example, the main crossover of the Andes between Argentina and Chile is still accomplished through the Paso Internacional Los Libertadores. Only recently the ends of some highways that came rather close to one another from the east and the west have been connected. Much of the transportation of passengers is done via aircraft.