A significant component of Justinian's project of imperial renovation was a massive building program, which was described in a book, the "Buildings", written by Justinian's court historian, Procopius. Justinian renovated, rebuilt, or founded anew countless churches within Constantinople, including Hagia Sophia, which had been destroyed during the Nika riots, the Church of the Holy Apostles, and the Church of Saints Sergius and Bacchus. Justinian also built a number of churches and fortifications outside of the imperial capital, including Saint Catherine's Monastery on Mount Sinai in Egypt, Basilica of Saint Sofia in Sofia and the Basilica of St. John in Ephesus.