Iglesia y Convento de San Francisco
A minor basilica and museum awarded UNESCO World Heritage status, this Baroque church was inaugurated in 1672 and is best known for its large system of catacombs. Uncovered in 1943, the subterranean passageways contain hundreds of thousands of bones, some of which are arranged in elaborate geometric patterns. Noteworthy features include the nave ceiling, painted in the mudéjar (Moorish-Spanish) style; the 17th-century monastery library, which houses more than 20,000 antique books; and the museum of religious artwork, which contains pieces by the workshops of Francisco Zurbarán and Peter Paul Rubens as well as a Peruvian interpretation of the Last Supper. Guided tours are available in both Spanish and English.