Colombia is bordered on the northwest by Panama, on the east by Venezuela and Brazil, and on the southwest by Peru and Ecuador. Through the western half of the country, three Andean ranges run north and south. The eastern half is a low, jungle-covered plain, drained by spurs of the Amazon and Orinoco Rivers, inhabited mostly by isolated tropical-forest Indian tribes. The fertile plateau and valley of the eastern range are the most densely populated parts of the country.
