A copy of this drawing by Chalgrin and a counterproof of the composition by Robert are at Besançon (V. Carlson, Hubert Robert, Drawings and Watercolors, exhib. cat., Washington, National Gallery of Art, 1976, figs. 4 and 5). The counterproof is probably taken from different drawing than the present one as the upper section is less finished. In the 1978 exhibition catalogue Victor Carlson dated the composition to shortly after Robert's arrival in Rome in 1756-57, comparing it to the first drawing in his catalogue, a view of the Loggia of Saint Peter's now in the Louvre.