Complex sentence: It is one of the oldest monasteries in the world, together with Saint Catherine's Monastery on Mount Sinai, which also lays claim to that title, and was established by the followers of Saint Anthony, who is considered to be the first ascetic monk.
Split into simpler sentences: It is one of the oldest monasteries in the world, together with Saint Catherine's Monastery on Mount Sinai, which also lays claim to that title. The Monastery of Saint Anthony was established by the followers of Saint Anthony, who is considered to be the first ascetic monk.