The Metropolitan Cathedral occupies the south side of Plaza 25 de Mayo and was begun in 1559, though it took two centuries to complete in fits and starts. The result is a hybrid of late Renaissance and baroque, dominated by a slim octagonal bell tower added in the 18th century. The pale stone facade carved with mestizo motifs is restrained from outside; the interior is lavish.
The cathedral's treasure is the Virgen de Guadalupe altarpiece — an originally modest painting that pilgrims have been encrusting with jewels for four hundred years. Gold, silver, diamonds, emeralds and pearls now cover almost every centimetre. The image is brought out in procession each September during the city's largest religious festival. The attached Cathedral Museum (entered separately, around the corner on Calle Ortiz) holds a serious collection of colonial religious painting, sculpture, and gold and silverware from the Potosí mints.