The left hand staircase has over it a little 17th century shrine to Our Lady of Sorrows, with a fresco of her in an arched niche. This is flanked by a pair of mediaeval epigraphs, one giving a list of relics provided by Pope Leo IV and the other recording the rebuilding by Pope Paschal II in 1111. Below the fresco is a slab of marble which used to belong to the high altar consecrated by Pope Paschal