Founded by the Spaniards in the early 16th century, it became the world's leading silver extraction centre in the 18th century. This past can be seen in its "subterranean streets" and the "Boca del Infierno", a mineshaft that plunges a breathtaking 600 meters. Its churches, La Compañía and La Valenciana, are considered to be among the most beautiful examples of Baroque architecture in Central and South America.