Elevation of the internal walls of the Lateran Baptistery; arch and windows at top, panelling and pilasters in middle, further panelling below. Copied after Sangallo’s drawing in the Barberini Codex (Rome, Vatican, Biblioteca Apostolica Vaticana, Barb. lat. 4424, fol. 31). The extant Paper Museum contains a total of 54 copies of architectural drawings from the Barberini Codex. The copies were produced by two draughtsmen, identified in dal Pozzo A.IX as the Codex Ursinianus Copyist and the Sangallo Copyist 2. Virtually all the copies are mechanical 1:1 replicas, probably traced. Annotations and measurements are usually omitted. For further, see A.IX, pp. 479-482. 

The Sangallo original is a half-elevation of one of the internal walls of the Lateran Baptistery, but the copyist extrapolates to make a complete elevation. The base moulding of the dado is missing but this may have been lost when the drawing was trimmed. The copyist is faithful to the original except for omitting Sangallo’s arbitrary S.P.Q.R. below the window. Calling the Baptistery Bagno is not unusual at this time: Giuliano da Sangallo does so on his plan copied on RCIN 919266 and the Speculum engraving, published c. 1560 by Lafréry refers to it as Balnei Laterani.

The opus sectile decorative scheme dating from Pope Sixtus III was lost in Urban VIII’s restoration c. 1630. The best evidence for what was there is found in the Speculum print. This agrees in broad terms with Sangallo’s drawing but differs in details such as the window, which appears as a lunette in the engraving. Further, the lowest order of panelling appears taller in Lafréry. It is difficult to determine which is the more accurate in the absence of other evidence.

The baptistery was originally built by Constantine to serve the Lateran Basilica, the cathedral of Rome, c. AD 320 (G.B. Giovenale, Il battistero Lateranense, 1929; G. Pellicioni, ‘Le nuove scoperte sulle origini del battistero Lateranense’, Atti della Pontificia Accademia Romana di Archeologia, Memorie ser. 3, XII, 1973, pp. 7–114). It was extensively remodelled by Pope Sixtus III (reg. 432–40), and again in the seventeenth century, under Pope Urban VIII. It remains in use. For a recent survey and analysis of the seventeenth-century restorations, see O. Brandt, ‘ Il battistero lateranense da Costantino a Ilario. Un riesame degli scavi’, Opuscula Romana 22–23, 1997–8, pp. 7–65.

The Lafréry print was almost certainly in the Paper Museum.

Numbering: 20

Annotations: [bottom centre, scribal hand] Una parte del Bagno di Constantino (‘A part of the Bath of Constantine’). 

Text adapted from Ian Campbell, The Paper Museum of Cassiano dal Pozzo: A Catalogue Raisonné. A.IX: Ancient Roman Topography, London, 2004, cat. 193.