THE HILL-FORT ON CONWAY MOUNTAIN, CAERNARVONSHIRE By W. E. GRIFFITHS, M.A., F.S.A., AND A. H. A. HOGG, M.A., F.S.A. I. INTRODUCTORY THE hill-fort on Conway Mountain (see Fig. 5 for location), known variously as Castell Caer Seion or Castell Caer Lleion,l comprises a large enclosure, protected by a single stone wall, and at the west end a smaller enclosure with more complex fortifications (Figs. 6 and 7). Both parts of the fort contain the foundations of round huts. During June 1951 the site was partially excavated under the supervision of the writers, assisted by Mr. D. B. Hague, A.R.I.B.A., and Mr. P. Smith, B.A., of the staff of the Royal Commission on Ancient Monuments in Wales and Monmouthshire, and with labour supplied by H.M. Ministry of Works. A small supplementary excavation was made in October 1952. Thanks are due to the Borough of Conway for permission to carry out the work, and to Mr. F. P. Jowett and Mr. D. M. Dixon, who also gave valuable assistance with the excavations. The conclusions reached may be summarized as follows. The site shows two periods of fortification, both within the latter part of the pre-Roman Iron Age in both periods the arrangement included a large and a small enclosure, but the details of the defence 1 Caer Seion appears to be the older and more genuine name. It is given as Caer Sion or Siion by Lewis Morris (1757) (Celtic Remains, ed. D. Silvan Evans, 1878, p. 393), but must be a good deal older since the form Sinnodune appears in Leland (1536-9) (Itinerary in Wales, ed. L. Toulmin Smith, 1906, p. 84). It is probably the Caer Seon mentioned in a ninth-century poem in the Black Book of Carmarthen (the manuscript of which is late twelfth century) (ed. J. Gwenogvryn Evans, 1907, p. 102) and in a poem of the early eleventh century which appears in the Book of Taliesin (the manuscript of which is c. 1275). The latter poem is edited and discussed in Anglesey Ant. Soc. Trans., 1941, pp. 23-30, by Sir Ifor Williams, who accepts the identification with Conway Mountain Gwenogvryn Evans' identification of the site with Caer Seiont (i.e. the Roman fort of Segontium at Caernarvon) (op. cit., p. xvii) seems unlikely. The alternative name appears as Mynydh Kaer Lheion in Gibson's edition of Camden's Britannia (1695), col. 670 and this is followed (in the form Castell Caer Lleion) by later writers such as Pennant (1773-6) (Tours in Wales, ed. 1883, III, p. 116) and Fenton (1804-13) ("Tours in Wales", Arch. Camb. Supple- ment, 1917, p. 202). This is probably due to confusion with Caer Lleon, the Welsh translation of Castra Legionum and the modern Welsh name of Chester.