The 6th century mosaic in San Lorenzo fuori le Mura (St Lawrence Outside the Walls) commemorates the eponymous saint, and the building of the church in his honour by Pope Pelagius II (r. 579-90).
The mosaic, which is set in the triumphal arch, cannot be seen from the nave; it can only be viewed from the choir. The explanation for this lies in the reorienting of the church in the 13th century.
Christ sits on the blue globe of the firmament; he holds a staff in his left hand and he raises his right hand in blessing. To the left stand St Peter, St Lawrence and Pope Pelagius II, who holds a model of the church. To the right stand St Paul, St Stephen (some of whose relics are kept in the church), and St Hippolytus, who, according to legend, was St Lawrence’s jailer.
At a lower level are the walled cities of Jerusalem and Bethlehem.