 On the walls of the nave is a large fresco cycle, recently restored, by the Lucchese Deodato Orlandi (early 14th century), which was commissioned by the Caetani family for the 1300 jubilee.In the lower part are "Portraits of Popes", from St. Peter to John XVIII (1303); the intermediate portion has thirty panels with "Histories of St. Peter's Life" (as well of those of St. Paul, Constantine and St. Sylvester), similar to those in the Old St. Peter's Basilica and to Cimabue's work at San Francesco in Assisi.In the upper area are portrayed the "Walls of the Heaven City", largely restored in the following centuries.