Cochabamba stands on the Rocha (ro´cha), a small tributary of the Guapai (gwah-pie´) River. Its population is about 30,000, mostly Indians and _mestizos_. The city is 8,400 feet above the sea, 291 miles north-northwest of Sucre, and 132 miles east-northeast of Oruro (o-roo´-ro). A newly constructed railway runs from Oruro to Cochabamba. The climate is mild and temperate, and the surrounding country fertile and cultivated. Trade is active; and in fact the city is one of the most progressive in Bolivia, in spite of its isolated situation. It is laid out regularly and contains many attractive buildings. The city has a university and two colleges, but they are poorly equipped. The name of the city of Potosí (po-to-see´) has become proverbial and “smacks of almost magical and unearthly wealth.” It possesses some of the most wonderful silver mines in the world. Founded in 1547, shortly after the first discovery of silver there by an Indian herder, it has since produced an enormous amount of the precious metal. One writer estimates the yield of the mines there as having been worth one billion dollars. Seven thousand mines have been started, of which seven hundred are being worked for silver and tin today. At one time the city had a population of 150,000, which has now dwindled to about 25,000. Potosí stands on a barren terrace about 13,000 feet above sea level, and is one of the highest towns in the world. It is 47 miles southwest of Sucre in a direct line. The famous Cerro Gordo (ser´-ro gor´-do; Spanish, ther´-ro gor´-do) de Potosí rises above the town to a height of 15,381 feet, a barren, white capped mountain, honeycombed with mining shafts. The town itself is laid out regularly. A large plaza forms the center, around which are grouped various buildings, such as the government house, national college, the old “Royal Mint,” dating from 1585, and the treasury. The city has a cathedral, which in part dates from early colonial times. The water supply is derived from a system of twenty-seven artificial lakes, or reservoirs, and aqueducts constructed by the Spanish government during the years of the city’s greatest prosperity. Oruro (o-roo´-ro) is an important mining town of about 20,000 people. During the colonial period this town was noted next to Potosí, for the richness and productiveness of its mines. The mines in the neighborhood are now worked principally, though not entirely, for tin. Oruro is 115 miles south-southeast in a direct line from La Paz. It stands 12,250 feet above sea level, and its climate is characterized by a short, cool summer and a cold, rainy winter. Oruro is the Bolivian terminus of the Antofagasta (ahn-toe-fah-gahs´-tah) Railway, the first constructed in Bolivia. In time the city promises to be one of the most important railway centers in the country.