To an approximate scale of 1:380

.TE[N]PLI. CESARIS. (‘of the Temple of Caesar’); uacuum. est. b. 44 [‘the interior space is 44 braccia’]; S[eptentrio]. (‘North’); [measurements]

• c.1513/14
  Datable to c.1513/14

Pen and brown ink and grey- brown over stylus lines and compass pricks

Bernardo della Volpaia

This domed pavilion of the fourth century CE, once part of the Horti Liciniani to the east of the city on the Esquiline Hill, has been erroneously known as the Temple of Minerva Medica since the late sixteenth century (Campbell 1984). It is labelled here, however, as the Temple of Caesar, a name it acquired by a roundabout route (Campbell 2011). In the medieval Mirabilia urbis Romae, it was described as a bath structure – the ‘Terme de Caluce’ – and Flavio Biondo, aware of this tradition, maintained in his Roma instaurata of the mid-1440s that ‘Caluce’ – or ‘Gallutii’ as he put it – was a corruption and conflation of the two names ‘Gaius’ and ‘Lucius’ (Biondo 1481, 2, chapter 24), which he maintained were those of the grandsons of the Emperor Augustus. He then concluded that the building was the ‘Basilica’ of Gaius and Lucius on the basis that, according to Suetonius, Augustus had built a basilica in their honour (Suetonius, Augustus, 29). Biondo’s identification of the building as a basilica was subsequently modified by Giuliano da Sangallo who, in the Codex Barberini, described it as a ‘temple’, presumably in the belief that round or polygonal buildings were temples rather than basilicas, but he maintained the association with Gaius and Lucius by stating that it was built in honour of ‘Chaio Luzio’. Giuliano’s understanding of the structure as a temple would then have provided the basis for its interpretation in the Coner drawing, except that the building is now a ‘Temple of Caesar’ (as indicated in the caption written in antique-inspired capitals), suggesting that it was not built by Caesar (i.e. Augustus Caesar) but dedicated to him.

The Coner plan broadly accords with the building as it survives today. It depicts the building with a decagonal core that is ringed with nine semi-circular alcoves and an entrance bay reached from a bi-apsidal vestibule with circular rooms to either side. Behind, to the left and right, are two great exedrae, their insides lined with niches, and to the rear is a pair of massive buttresses. Modern-day archaeology generally confirms this layout (Barbera–Magnani Cianetti 2019), although there appears to have been only one buttress at the rear, while the vestibule was bordered not by circular spaces but by semi-circular ones, as shown in a subsequent plan published by Palladio. The Coner plan also departs from the realities of the building in certain other details, and, moreover, what it depicts on one side does not always correspond with what it shows on the other, which can all be explained by considering how the plan was probably arrived at.

It has been established that the Coner plan and the two drawings of the building next to it are related to a similar set included by Giuliano da Sangallo in his Codex Barberini (Ashby 1904), and that the Coner plan is by no means a straightforward copy of the Barberini plan (Campbell 1984; Nesselrath 1992). Rather, it can be read as a critique, the Barberini plan being selectively improved in several specific ways to make it closer to the building’s observable realities. For example, the isolated areas of walling between the central space and the two flanking exedrae are made far more massive and have flat rather than curving faces on their outer sides, the junctions of the exedrae with the central space are adjusted, the number of niches in the exedrae are reduced from thirteen to eleven, the shapes of the niches in the alcoves of the central pavilion (only one shown) are changed from round to rectangular; column screens are inserted into the vestibule, and a doorway is inserted into the rear of the semi-circular alcove at the end. The Coner drawing, besides noting the central pavilion’s impressive interior diameter (44 braccia), also provides a far more complete set of measurements, and even ‘corrects’ some of those in the Codex Barberini, such as by adjusting the depth of the right exedra from 18 braccia to 18½ braccia.

Other discrepancies, however, are a little less easy to explain. One relates to the semi-circular alcoves flanking the one at the end which, in the Barberini plan, are both encased so that the external curvature corresponds with the rotunda’s overall circumference, but which, in the Coner plan, differ from one another, the right-hand alcove being encased but the left-hand alcove having an exterior that follows its internal shape. This departure from the Sangallo drawing corresponds at least to an extent with the surviving archaeological remains, insofar as the left-hand alcove is represented correctly while several of the others were embedded in the wall-thickness of the rotunda, and suggests that the intention was to represent the left-hand alcove correctly. A second discrepancy is seen in the frontal portion of the edifice, which was already in a ruinous state of preservation. In the Barberini plan, large and irregularly shaped spaces for which evidence survives are shown on both sides behind the circular rooms at the front, whereas, in the Coner plan, a similar irregularly shaped space is shown on the right, but a rectangular space with an adjacent circular staircase is indicated on the left. This difference is possibly explained, again, in relation to the surviving remains shown in modern-day plans, and would appear to represent a brave attempt to make sense of ancient modifications to the original structure, when part of the previously-irregular space could well have been transformed into a rectangular one (Barbera–Magnari Cianetti 2019, p. 97), although this attempt may not have been the initiative of the Coner draughtsman. A very similar interpretation of this part of the building is seen in a slightly later drawing in Montreal, so it seems most likely that both the Coner and Montreal depictions were based on a now-lost drawing that had been produced previously. The possibility, however, that the Coner drawing was itself based, at least in part, on an actual site survey is indicated by the inclusion of a compass bearing, for ‘north’, in its bottom-left corner.

The Coner drawing thus appears to show successive stages in the improvement of the Barberini prototype. At the outset, a series of changes were identified that brought the Sangallo plan more closely into line with the building’s physical realities, and this corresponds with the right half of the Coner plan. It then provided a basis for further investigations, corresponding with the left half of the Coner plan, when the building and its surviving fabric were scrutinised even more exactingly, and further modifications were identified. Not all the differences were ‘improvements’, however. Notably wrong was the decision to make all the semi-circular alcoves the same size even though the Barberini drawing had established that the rear alcove was a little wider than the rest (10¾ braccia rather than 10⅓ braccia). Nevertheless, the efforts expended on this particular building were still impressive, and can be thought of, like the drawing’s positioning in the codex immediately after the plan of the Pantheon and before that of the Basilica of Maxentius, as a mark of its accrued reputation. As Flavio Biondo put it, ‘after the Pantheon there is nothing in the city more excellent’ (Quo post Pantheon nullus nunc in urbe visitur excelsior).

RELATED IMAGES: [Giuliano da Sangallo] Rome, BAV, Barb. lat. 4424 (Codex Barberini), fol. 6r (Hülsen 1910, 1, p. 12)

OTHER IMAGES MENTIONED: [Anon.] Montreal, CCA, Roman Sketchbook, fol. 52r; Palladio 1570, 4, p. 40

OTHER DRAWINGS IN CODEX CONER OF SAME SUBJECT: Fol. 9r/Ashby 15 (Drawing 2 and 3 on this page)

Ashby 1904, p. 16
Ashby 1913, pp. 191–92
Campbell 1984, pp. 283–87
Günther 1988, p. 338
Nesselrath 1992, p. 147
Census, ID 44004

Drawing

Digitisation of the Codex Coner has been made possible through the generosity of the Census of Antique Works of Art and Architecture Known in the Renaissance, Berlin.

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