Standing behind high walls on an impressive site at the foot of Mt Sinai, this is one of the oldest working monasteries in the world. It was built in the 6C, by order of Emperor Justinian, to protect believers who came to pray at the site where the prophet had seen the Burning Bush. In the church, note the relics of St Catherine, the forest of icons and the fine 6C mosaic. The library contains 3 500 volumes, the world's largest collection of early codices and manuscripts after the Vatican's.