The monastery of San Juan de la Peña is a religious complex in the town of Santa Cruz de la Serós. It is to the southwest of Jaca, in the province of Huesca, Spain. It was one of the most important monasteries in Aragon in the Middle Ages. Its two-level church is partly carved in the stone of the large cliff that is over the foundation. San Juan de la Peña means "Saint John of the Cliff".