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ISCA (Caerleon) Monmouthshire, S Wales.

The base fortress of Legio II Augusta, which had participated in the invasion of Britain, A.D. 43; founded by Julius Frontinus during the conquest of Wales (Tac. Agric. 17) in 74-75. Now a village on the river Usk, 4.8 km upstream of Newport (Mon.), Caerleon has been extensively excavated since 1926. Most of the plan can be reconstructed, but only the amphitheater and a centurial barrack in the W corner, together with parts of the adjacent defenses, are visible today.

The fortress occupies a position very similar to that of Legio XX V. V. at Chester—at the roots of the Welsh peninsula, on a navigable estuary for ease of supply, but above danger of flooding. Between them, the two fortresses maintained the military occupation of Wales, and some of the auxiliary forts at important valley junctions provide evidence of a legionary connection (brick stamps, inscriptions). The tactical position of Caerleon is particularly good since it lies in a wide bend of the Usk and is additionally protected by a small tributary on the E. To the NW rises a hill crowned by a hate Iron Age hill-fort. Running water was carried by 20 cm head pipes from an unknown source.

The fortress is a rectangular enclosure with rounded corners, oriented NW-SE and 90 by 18 m. an area of 20.6 ha. The defenses first consisted of a clay bank formed of upcast from a single ditch 9 m wide; the rampart was strengthened with timbering, but nothing is known of the gateways and turrets of the initial period. In the 2d c. the bank was cut back, and a wall (still in parts visible) built, with a double gateway in each side; there were internal turrets at intervals of ca. 45 m. Extensive rebuilding at the S corner of the wall may be related to damage sustained during a revolt of the Silures while the legion was supporting Albinus in Gaul, in 196-197.

The interior is divided into three lateral zones by the via principalis (between the NE and SW gates) and the via quintana. In the center of the middle, or administrative zone stood the headquarters (principia): it is mostly under the present church, but part of the basilica (64.8 x 26.85 m internally) was excavated in 1968-69. The roof was supported by lofty colonnades of Bath stone, in front of the N row of which there had been inscribed plinths for statues, two of bronze (only scraps remain): cf. the statues erected in a similar position at Lambaesis. The building was dismantled at the end of the 3d c. On its right side, three of the five houses for primi ordines centurions, together with parts of the corresponding 10 barracks for the milhiary first cohort, have been excavated. On the left side, parts of six barracks for a quingenary cohort are known, together with stabling for the 120 equites, or scouts, of the legion. Behind the principia lay the palace of the legate (praetorium), with an internal oval court as at Xanten, but approached through a large basilica for public audience. On the right side of the praetorium is a great basilica exercitatoria, for drill in wet weather; adjacent are some rows of magazines. The nature of buildings in an insula farther SW are as yet unknown. On the left side of the pinetorium is a large courtyard building identified as workshops, consisting of large halls or stores; residential accommodation projects into the courtyard. The contents of an insula farther NE are unknown.

The retentura is entirely given over to centurial barracks arranged longitudinally and accommodating two quingenary cohorts; 12 barracks, on either side of the decumanus, led to the NW gate. The barracks measured ca. 72 by 12 m, about a third allocated to the centurion and the rest divided into 12 double cubicles for the men.

The praetentura is bisected by the via praetoria leading from the SE gate to the headquarters. Inside the SE defenses another long range of 24 barracks completes the accommodation for the 10 cohorts of the legion. The remaining ground on the SW side of the praetentura has not been much explored; it is likely that granaries occupy part of it. On the NE side, recent excavation has revealed parts of the hospital and the large internal baths, both of which were demolished about the end of the 3d c. The hospital consists of rows of small wards arranged around three sides of a square court, with a second concentric range within; a large operating theater projected into the court from the fourth and SE side. The baths comprised a large basilica (63.3 x 23.4 m) opening from the via principalis, a frigidarium with several piscinae, and heated accommodation, the most important elements of which (calidarium, etc.) are inaccessible. On the SW lay a palaestra with porticos on three sides, containing a pool (40.5 x 5.4 x ca. 1.2 m) reminiscent of the palaestra of Herculaneum.

The entire block of internal buildings is divided from the defenses by a wide street. Various turrets had cookhouses built in front of their ground-floor entrances and numerous rampart magazines are known. Latrines have been excavated in the S and W corners and probably existed on the E and N. Some of the principal buildings were erected in stone from the beginning, but the barracks and the hospital were first built of timber on cobble footings. The stone replacements are of 2d c. date, and there was widespread rebuilding and repair in the early 3d c.

The environs of the fortress include elements of a small vicus cannabarum on the SW, which seems never to have reached urban proportions, perhaps because the cantonal capital of the Silures (Venta Silurum) was not far distant. Shops, a mansio (?), and other buildings are known, while temples of Mithras, Jupiter Dolichenus, and Diana are epigraphically attested. The area is divided by a continuation of the main street down to the Usk, where 3d c. wharves have been excavated; the civil settlement is separated from the fortress, NW of this road, by a walled parade ground (ca. 150 x 207 m), and on the SE side by the amphitheater (80.1 x 66.6 m; the arena, 55.2 x 40.95 m). The structure is partly set into the ground, the upcast being revetted by stout walling as a basis for the wooden seating. There are four principal entrances, two on the short axis with boxes above, and four subsidiary ones; all, except the two that led directly into the arena, had dens at the level of the arena. A large bath house is adjacent, and another is known on the SE side of the fortress. On the S side of the Usk and along roads leading W and NE there were cemeteries, including at least two mausolea belonging to burial clubs; cremation was the predominant rite.

The finds are housed in the Legionary Museum of Caerleon (branch of the National Museum of Wales) and at the National Museum in Cardiff.


J. E. Lee, Isca Silurum (1862)I; G. C. Boon & C. Williams, Plan of Caerleon (1967) with bibl.MP; Boon, Isca: the Roman Legionary Fortress at Caerleon, Mon. (1972)MPI

See also excavation reports: JRS 16ff (1926ff) summariesPI; Archaeologia 78 (1928) amphitheaterMPI; Archaeologia Cambrensis 84ff (1929ff)MPI; Monmouthshire Antiquary 1 (1961-64)PI.


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