We are grateful to Professor David Marshall for confirming the attribution to Giovanni Paolo Panini on the basis of photographs. Professor Marshall has suggested a dating of around 1716-1718, based on the angular handling of the relief and the striking similarity of the present composition to the Architectural capriccio with the Pyramid of Cestius in the Galleria Manzoni, Milan, which probably dates to around 1718-1720 (see F. Arisi, Gian Paolo Panini e i fasti della Roma del '700, Rome, 1986, p. 283, no. 121). It can also be compared to The sermon of the apostle in the Ashmolean Museum, Oxford (see op. cit., p. 287, no. 130).