Bones—including thousands of human skulls—are piled in eerie geometric patterns in the catacombs beneath this Franciscan monastery. This was the city's first cemetery, and the underground tunnels contain the earthly remains of some 75,000 people, which you visit on a tour (available in English). The Convento de San Francisco is one of Lima's most visited sites, mostly because of the catacombs. But its church, the Iglesia de San Francisco, is the best example of what is known as "Lima Baroque" style of architecture. The handsome carved portal would later influence those on other churches, including the Iglesia de la Merced. The central nave is known for its beautiful ceilings painted in a style called mudejar (a blend of Moorish and Spanish designs). On the tour, you'll see the monastery's immense collection of antique texts, some dating back to the 17th century.