The lost basilica of the Holy Apostles in Costantinople in a western medieval illumination. Built by Emperor Constatine and rebuild by Justinian I, Holy Apostles was 2nd in importance and magnificence after Hagia Sophia also because it was the burial of many emperors and patriarchs. During the 4th Crusade, the church was pillaged by Venetians and, at the time of Ottoman conquest, it was partially in ruins. Sultan Mehmed II built over it the Fatih Mosque