West of the aqueduct, on Istanbul's fourth hill, is the Fatih Mosque (Fatih Camii, Sultan Mehmet Camii), built in 1463-71 on the site of the church of the Holy Apostles (founded by Constantine the Great and rebuilt by Justinian) and almost completely rebuilt after an earthquake in 1765. It is the holiest mosque in Istanbul after the Eyüp Mosque. In the first türbe behind the mosque is the Tomb of Sultan Mehmet.