The two main areas of Spanish settlement after 1550 were Mexico and Peru, the sites of the Aztec and Inca indigenous civilizations. Equally important, rich deposits of the valuable metal silver. Spanish settlement in Mexico largely replicated the organization of the area in preconquest times while in Peru, the center of the Incas was too far south, too remote, and at too high an altitude for the Spanish capital. The capital Lima was built near the Pacific coast. The capitals of Mexico and Peru, Mexico City and Lima came to have large concentrations of Spanish settlers and became the hubs of royal and ecclesiastical administration, large commercial enterprises and skilled artisans, and centers of culture. Although Spaniards had hoped to find vast quantities of gold, the discovery of large quantities of silver became the motor of the Spanish colonial economy, a major source of income for the Spanish crown, and transformed the international economy. Mining regions in both Mexico were remote, outside the zone of indigenous settlement in central and southern Mexico Mesoamerica, but mines in Zacatecas (founded 1548) and Guanajuato (founded 1548) were key hubs in the colonial economy. In Peru, silver was found in a single silver mountain, the Cerro Rico de Potosí, still producing silver in the 21st century. Potosí (founded 1545) was in the zone of dense indigenous settlement, so that labor could be mobilized on traditional patterns to extract the ore. An important element for productive mining was mercury for processing high-grade ore. Peru had a source in Huancavelica (founded 1572), while Mexico had to rely on mercury imported from Spain.