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Bill Thayer

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 p40  Arcus Neroniani

Article on pp40‑41 of

Samuel Ball Platner (as completed and revised by Thomas Ashby):
A Topographical Dictionary of Ancient Rome,
London: Oxford University Press, 1929.

Arcus Neroniani: * a branch of the Aqua Claudia (q.v.) built by Nero (Frontinus, de aquis I.20, II. 76, 87) from Spes Vetus to the temple of Claudius on the Caelian, a distance of two kilometres. For the greater part of its irregular line remains of it are preserved. Near S. Stefano Rotondo it divided, and one section ran towards the Aventine, ending near the church of S. Prisca (LF 35; cf. CIL VI.3866 = 31963). The arches have a span of 7.75 metres and the piers are 2.30 long and 2.10 thick, the maximum height being 16 metres.​1 The brickwork is very fine and interesting, as Rivoira points out. Skeleton tile ribs are first seen  p41 in these arches​2 (RA 71‑73; cf. also BC 1926, 265). Where the aqueduct crossed streets, the arches were wider and more imposing (see Arcus Basilidis, Arcus Dolabellae et Silani). The valley between the Caelian and the Palatine was traversed by an aqueduct, perhaps built by Domitian, with two tiers of arches, which may have carried a syphon. right-angled turn at the bottom of the valley makes this a little doubtful. The pipe, 30 cm. in diameter, which is generally associated with the syphon, would not have stood the pressure; while if, as at Lyon, small pipes were used, they might easily have become choked with deposit. Severus reinforced the arches of Nero (CIL VI.1259, where they are called arcus Caelimontani), including the line of arches across the valley just mentioned (LA 364‑374; LS III.79; JRS 1919, 187; ZA 147‑149). For a branch which crossed the Tiber, see Fornix Augusti.

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A view of part of the Neronian arches from the SW.

To our left, the mons Caelius, towards which the aqueduct appears to rise (an effect of perspective). The Porta Maggiore is about 200 m away, offscreen right, slightly behind the arches. See also this endlong view.

The aqueduct is frequently mentioned in the post-classical period. Forma Claudiana in Eins. 8.17, clearly refers to it (Forma Lateranense, ib. 7.17; 9.3; but contrast 2.6), and it was restored by Hadrian I (LPD I.504). In a document of 978 (Reg. Subl. p161) there is a mention of a domus in qua est oratorium martyrum Cosmae et Damiani quinta Romae regione II iuxta formam Claudiaº and this oratory, which is mentioned among the boundaries of S. Erasmo on the Caelian, which lay to the west of S. Stefano Rotondo (HCh 249), is probably the same as S. Cosmae et Damiani ubi dicitur asinum frictum (Reg. Subl. p224).

Asinus frictus may, like ursus pileatus, be the name of an ancient road, derived from a shop sign. The name is, however, also found in the neighbourhood of Rome (HCh 239) on the via Ostiensis (T. X.32).

The church of S. Nicolas de Formis, near S. Stefano Rotondo, took its name from this aqueduct (HCh 398), and so did S. Daniel and SS. Sergius and Bacchus, near the Lateran (ib. 248, 462), and S. Thomas de Formis close to the Arcus Dolabellae et Silani (ib. 491).

The arcus Formae mentioned in the Ordo Benedicti (Jord. II.665; Lib. Cens. Fabre-Duchesne II.154; HCh 258‑259) is no doubt the Arcus Iohannis Basilii (q.v.).

The Authors' Notes:

1 See Livellazione, p16, fig. 2, where the bottom of the specus in the Piazza S. Giovanni in Laterano is determined at 63.13 metres above sea-level.

2 This is, however, doubtful, as the greater part of the original structure is enclosed or replaced by the work of Septimius Severus, to which these tile ribs belong.

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Page updated: 11 Jul 24