Nariño Department in the context of Cordillera Occidental, Colombia

The Andean region, located in central Colombia, is the most populated natural region of Colombia. With many mountains, the Andes contain most of the country's urban centers. They were also the location of the most significant pre-Columbian indigenous settlements as well as the region with the most European influence due to immigration from the colony to the present day. 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.

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, approximately 1,000 m to 2,000 m) and tierra fría (cold land, 2,000 m to 3,200 m), which include the most productive land and most of the population; and the alpine conditions of the zona forestada (forested zone, 3,200 m to 3,900 m), páramos (3,900 m to 4,600 m) and tierra helada (frozen land, 4,600 m and above).

The Cordillera Occidental (English: Western Ranges) is the lowest in elevation of the three branches of the Colombian Andes. The average altitude is 2,000 m (6,600 ft) and the highest peak is Cerro Tatamá at 4,100 m (13,500 ft). The range extends from south to north dividing from the Colombian Massif in Nariño Department, passes north through Cauca, Valle del Cauca, Risaralda, Chocó, and Caldas Departments to the Paramillo Massif in Antioquia and Córdoba Departments. The cordillera is paralleled on the east by the Cauca river. From this massif the range divides further to form the Serranías de Ayapel, San Jerónimo and Abibe. Only to recede into the Caribbean plain and the Sinú River valley.

It is a direct continuation of Cordillera Occidental of Ecuador.

Galeras (Urcunina among the 16th-century indigenous people) is an Andean stratovolcano in the Colombian department of Nariño, near the departmental capital Pasto. Its summit rises 4,276 metres (14,029 ft) above sea level. It has erupted frequently since the Spanish conquest, with its first historical eruption being recorded on December 7, 1580. A 1993 eruption killed nine people, including six scientists who had descended into the volcano's crater to sample gases and take gravity measurements in an attempt to be able to predict future eruptions. It is currently the most active volcano in Colombia.

Cauca Department (Spanish pronunciation: [ˈkawka], Spanish: Departamento del Cauca) is a department of Southwestern Colombia. Located in the southwestern part of the country, facing the Pacific Ocean to the west, the Valle del Cauca Department to the north, Tolima Department to the northeast, Huila Department to the east, and Nariño Department to the south. Putumayo and Caqueta Departments border the southeast portion of Cauca Department as well. It covers a total area of 29,308 km (11,316 sq mi), the 13th largest in Colombia. Its capital is the city of Popayán. The offshore island of Malpelo belongs to the department. It is located in the southwest of the country, mainly in the Andean and Pacific regions (between 0°58′54″N and 3°19′04″N latitude, 75°47′36″W and 77°57′05″W longitude) plus a tiny part (Piamonte) in the Amazonian region. The area makes up 2.56% of the country.

The Altiplano Nariñense or Nariño plateau is an area of flat lands located on the eastern mountain range of the Colombian Andes cordillera, in the departments of Nariño and Putumayo, in southern Colombia. The region comprises three fairly distinguishable flat areas such as the Túquerres and Ipiales plateau, the Atriz valley and the Sibundoy valley. It is a region of great demographic density where there are numerous urban centers, among which the cities of San Juan de Pasto, Ipiales and Túquerres stand out.

The average altitude is 2,700 meters above sea level. It has a mountain climate, which varies with altitude, with temperatures ranging between 10 and 23 degrees Celsius.

The Colombian Massif (from the Spanish Macizo Colombiano), also known colloquially as Nudo de Almaguer, refers to a group of mountains within the Andes of south central Colombia. The massif is mainly within the area of the Cauca, Huila, and Nariño Departments. To the south is the Pasto Massif and to the north begins the Central and Eastern Andes.