The Papal Basilica of St Paul Outside the Walls (Italian: Basilica Papale di San Paolo fuori le Mura), commonly known as St Paul-without-the-Walls, is one of four churches that are the great ancient major basilicas. The basilica was founded by the Roman Emperor Constantine I over the burial place of Saint Paul, where it was said that, after the Apostle’s execution, his followers erected a memorial, called a cella memoriae. This first edifice was expanded under Valentinian I, in the 370s. In 386, Emperor Theodosius I began the erection of a much larger and more beautiful basilica with a nave and four aisles with a transept; the work including the mosaics was not completed till the pontificate of Leo I (440-461). In the 5th century it was even larger than the Old St. Peter’s Basilica.