According to legend, St Peter lost the bandage (fasciola) bound around his leg to cover the sores caused by the chains which had held him in the Mamertine prison on this site as he fled Rome terrified by the fate which awaited him; a church later grew up around the site. Rebuilt in the early 9C, the church was restored in the 15C and in the late 16C the relics of St Nereus and St Achilleus were transferred here by Cardinal Baronio, Clement VIII's confessor, who had a great devotion for these saints.