This bright-yellow Franciscan monastery and church is most famous for its bone-lined catacombs (containing an estimated 70,000 remains) and its remarkable library housing 25,000 antique texts, some of which predate the conquest. Admission includes a 30-minute guided tour in English or in Spanish. Tours leave as groups gather.

This baroque structure has many other treasures: the most spectacular is a geometric Moorish-style cupola over the main staircase, which was carved in 1625 (restored 1969) out of Nicaraguan cedar. In addition, the refectory contains 13 paintings of the biblical patriarch Jacob and his 12 sons, attributed to the studio of Spanish master Francisco de Zurbarán.