Saint Catherine’s Monastery is an Orthodox monastery on the Sinai Peninsula. It is the smallest dioceses and the oldest Christian monastery still in use in the world. It also houses a rich collection of icons and precious manuscripts. It lies in the foothills of Moses Mountain 5012 feet above sea level in the city of Saint Catherine in Egypt's South Sinai Governorate. Set beneath the mountain where God revealed the Ten Commandments to Moses.
The monastery was built by order of Emperor Justinian I (reigned 527-565), enclosing the Chapel of the Burning Bush ordered to be built by Helena, the mother of Constantine I, at the site where Moses is supposed to have seen the burning bush; the living bush on the grounds is purportedly the original. It is also referred to as "St. Helen's Chapel." The site is sacred to Christianity and Islam.
The monastery is a UNESCO World Heritage Site. According to the UNESCO report, this monastery is one of the oldest working Christian monasteries in the world together with the Monastery of Saint Anthony, situated across the Red Sea in the desert south of Cairo, which also lays claim to that title. The monastery library preserves the second largest collection of early codices and manuscripts in the world, outnumbered only by the Vatican Library. Its strength lies in Greek, Arabic, Armenian, Hebrew, Georgian, Syriac and old Udi texts. The Codex Sinaiticus, now in the British Library, left the monastery in the 19th century for Russia, in circumstances that are now disputed.