During the coldest winter months their communications are much easier with Spain than through the snowclad passes leading into Ariege.
Fully one-half of its length is through the mountainous districts of central Bolivia, where it is fed by a large number of rivers and streams from the snowclad peaks, and may be described as a raging torrent.
The snowclad Andi ridge, belonging to the system of transverse upheavals which cross the Caucasus, branches off the latter at Borbalo Peak (10,175 ft.), and reaches its highest altitudes in Tebulosmta (14,775 ft.) and Diklos-mta (13,740 ft.).
Although only one or two peaks reach the line of perpetual snow, several of the loftiest summits are snowclad during the greater part of the year.
After flowing southward along the base of the high Andes for a short distance and receiving a number of torrents from the snowclad heights, it turns south-eastward across the plain and enters the Maranon about 70 m.