The area east of the Andes includes about 699,300 square kilometers, or three-fifths of the country's total area, but Colombians view it almost as an alien land. The entire area, known as the eastern plains, was home to only 2 percent of the country's population in the late 1980s (see fig. 3). The Spanish term for plains (llanos) can be applied only to the open plains in the northern part, particularly the piedmont areas near the Cordillera Oriental, where cattle raising is practiced.

The region is unbroken by highlands except in Meta Department, where the Macarena Sierra, an outlier of the Andes, is of interest to scientists because its vegetation and wildlife are believed to be reminiscent of those that once existed throughout the Andes. Many of the numerous large rivers of eastern Colombia are navigable. The Río Guaviare and the streams to its north flow eastward and drain into the basin of the Río Orinoco, the largest river in Venezuela. Those south of the Río Guaviare flow into the basin of the Amazon. The Río Guaviare divides eastern Colombia into the llanos subregion in the north and the tropical rainforest, or selva, subregion in the south.

Data as of December 1988