Royal Monastery of San Juan de la Peña

The monastery of San Juan de la Peña is a religious complex in the town of Santa Cruz de la Serós, at the south-west 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 partially carved in the stone of the great cliff that overhangs the foundation. San Juan de la Peña means "Saint John of the Cliff".

The lower church includes some mozarabic architectural surviving elements, although most of the parts of the monastery are Romanesque. After the fire of 1675, a new monastery was built. The old monastery was declared a National Monument on 13 July 1889, and the new monastery in 1923. In the 11th century the monastery became part of the Benedictine Order and was the first monastery in Spain to use the Latin Mass.