Pisac celebrates the Virgen del Carmen festival (July 16-18) with nearly as much enthusiasm as the more remote and more famous festival in Paucartambo. It's well worth visiting Pisac during the festival if you are in the area. The Pisac ruins are some of the finest and largest in the entire valley. Despite the excellent condition of many of the structures, little is conclusively known about the site's actual purpose. It appears to have been part city, part ceremonial center, and part military complex. It might have been a royal estate of the Inca emperor (Pachacútec). It was certainly a religious temple, and although it was reinforced with the ramparts of a massive citadel, the Incas never retreated here to defend their empire against the Spaniards (and Pisac was, unlike Machu Picchu, known to Spanish forces).