Room 17 of the Pinacoteca contains the preparatory models made of clay mixed with straw on a framework of iron and cane for the bronze figures of St Peter's Chair. They are works of great documentary and artistic interest both because of the high quality of the models that testifies as to the intervention of Bernini, and because of the fact that the forms for fusion were drawn from them. The models for the Chair include the heads of St Athanasius and St John Chrysostom as well as the figures of angels. The mighty monument in marble, stucco and gilded bronze that decorates the area of the apse of St Peter's Basilica was constructed by Bernini and his assistants in the years 1658-1666 during the pontificate of Alexander VII (pontiff from 1655 to 1667). Its creation was a result of the decision to transfer the much venerated relic of the wooden chair on which, according to medieval tradition, St Peter used to sit to instruct the Christians (actually it is the throne that the emperor Charles the Bald gave to Pope John VII in 875) from the Baptismal Chapel to the apse of the Basilica. The great bronze throne, in which the wooden chair is preserved, is silhouetted against the clouds, surrounded by angels and by four large figures of the Doctors of the Church (St Ambrose, St Augustine, St Athanasius and St John Chrystostom).