Erfurt was the young Luther's spiritual home. In 1505 he graduated with a Masters from the university's faculty of philosophy. It is said that a violent storm close to Erfurt that same year prompted him to become a monk at the Augustinian monastery in gratitude for his survival. Martin Luther stayed in Erfurt until 1511 and was ordained as a priest in the cathedral. Even after he had left the city, he often returned to preach to enthusiastic crowds, in the university church (St. Michael's) for example. It is more than 500 years since Luther was a student at the collegium maius, the old Erfurt university's main building, which is now being restored. On 10 November every year, Erfurt celebrates Martin Luther's birthday and remembers St. Martin with the St. Martin's Festival on Domplatz.