Dunaengus — Cill Mhuirbhigh

Spectacularly perched at the edge of the sheer sea-cliffs on the SW side of Inis Mór, Dún Aonghasa, a multiperiod fort, commands extensive views of the Atlantic seaways off the W coast, as well as across the island itself and as far as the Twelve Bens mountain range in Connemara to the N, and the Cliffs of Moher on the Clare coast to the SE. It has been a magnet for antiquarians since the early 19th century and has been studied by Petrie (1972), O'Donovan (O'Flanagan 1927a, Vol. 3, 197-212) and Westropp (1895, 256-9), among others. More recently it was the core focus of 'The Western Stone Forts Project', which was undertaken by the Discovery Programme and during the course of which four seasons of excavations were carried out between 1992 and 1995 (Cotter 2012). The project found that the fort had a long history from its earliest occupation in the Late Bronze Age (c. 1000 BC) to its abandonment in the early medieval period (c. AD 1000). The initial fort was interpreted by Cotter (ibid., vol. 1, xxiii, Fig. 3.7; vol. 2, 227) to be a hillfort, which was roughly D-shaped in plan (c. 360m NW-SE; c. 240m NE-SW overall) and enclosed an area of 5.8ha (14 acres) (ibid., vol. 1, 53). It was defined by three drystone double-faced limestone walls with rubble cores (av. Wth 2m) that formed an inner (wall 1), middle (wall 2a) and outer enclosure (wall 4) (ibid., vol. 1 55, Fig. 3.7). The U-shaped inner enclosure (c. 51m NW-SE; c. 46m NE-SW) occupied the highest elevation of the plateau. Due to erosion of the cliff it was unclear whether the enclosing wall continued beyond the current cliff edge or ran across the cliff face. The roughly level subrectangular middle enclosure (c. 100m NW-SE; c. 84m NE-SW) did not surround the inner enclosure as is the usual case in comparable Irish hillforts. Instead both enclosures were conjoined, with the middle enclosure extending off the inner one to the E (ibid., vol. 1, 89-129, 135-42; vol. 2, 239). The outer enclosure lay some distance downslope, encompassing both the inner and middle enclosures. In contrast to the latter enclosures, its interior was rugged and inhospitable. However, its enclosing wall (av. H 1.4m; base Wth 2.1m along W and N flanks) was the best preserved part of the original defences. Though a later field wall overlay its E flank (max. H 0.8m; Wth 1.75-2.1m), a substantial portion of the original wall foundations survived in situ and this section of the wall appeared to be the only element of the fort that was not subsequently rebuilt (ibid., vol. 2, 232). An internal terrace was built against the wall and traces of it are evident along its wall-face at W and NW. A lintelled entrance at N provided access; the latter feature is almost directly opposite the NE entrance in the middle enclosure (ibid., vol. 1, 72-88). A major refurbishment and remodelling of the fort took place some time in the early medieval period when its defensive aspects were greatly improved (ibid., vol. 1, 167-226). This involved the strengthening of the existing walls of the inner and middle enclosures, the reconfiguring of the line of the middle enclosure (wall 2b) and the construction of a chevaux-de-frise and another wall (wall 3) outside the middle enclosure (ibid., vol. 1, xxiii; Fig. 6.102). The monumental form of the inner enclosure is largely the result of these works. Its massive wall (max. H 4.9m; base Wth 3.5-5.8m), which has a marked external base-batter (Wth 0.8m), was increased in width by the addition internally and externally of a number of thin vertical skins of masonry (ibid. vol. 2, 272). Two internal terraces were built below the parapet. Both are accessed by two flights of vertical steps that are set into the thickness of the wall, and a third flight which is set sidelong to it; the latter flight to the upper terrace has collapsed. Other features in the wall include a wall chamber (ibid., vol. 1, 151) at NW and the entrance passageway at NE. Within the interior a natural rectangular platform of limestone (H 0.6m; 7m x 5m) visible at the cliff edge appears to have been deliberately left in place (ibid., vol. 1, 54-5, 151). When the NW section of the original wall of the middle enclosure was removed, the enclosure wall (max. H 4m; base Wth 1.3-3.8m) was then extended to the W and around the W flank of the inner enclosure. A pronounced kink in the wall at N indicates where the two sections meet. A blocked-up lintelled entrance along the N stretch, to the E of the kink, is probably the original entrance; another entrance at NE is secondary. The entrance gap in the later walling is also probably not an original feature. Both wall sections are terraced and access to the terrace is gained by a sidelong flight of steps and a rebuilt set of steps on each side of the NE entrance gap. The free-standing wall (Wall 3) (L 63m; av. H 2m; base Wth 1.5-2.6m), which has been the subject of much previous discussion regarding where it fits into the scheme (ibid., vol. 2, 233), curves around the middle enclosure from W to NNW. It may originally have continued further to the S but there is no evidence on the ground to indicate that it extended further to the E. Remains of terracing are visible on its internal face and an entrance gap is opposite that in the middle wall. The chevaux-de-frise curving around this wall and the middle enclosure is the most impressive example of this type of defensive structure in Europe. The sheer scale of its undertaking is remarkable. It would have formed an almost impenetrable obstacle to anyone approaching the outer defences of the fort as it consists of a band of densely set pillars, which cover an area of 6,500 square metres and vary in width from 15m to 38m. It is best preserved at NW where the pillars are up to 1.75m high. Many of the larger examples weigh up to half a ton and it is likely they were prised off the surrounding limestone pavement and then swivelled into an upright position. There was no attempt to socket the stones and they were supported and held in place with quarry rubble. Weathering has given many of the pillars a jagged profile (ibid., vol. 2, 197, 202, 271). Traces of an external kerb, made up of contiguous or recumbent stones, defines it outer limits. A walled avenue at NE is the only means of access through it and it leads to the NE entrance in the middle enclosure (ibid., vol. 1, 55-8). Cotter (ibid., vol. 1, 167; vol. 2, 272) noted that the construction of the chevaux-de-frise considerably changed the character of the fort as it effectively cut off the sloping outer enclosure from the middle and inner enclosures and significantly reduced the size of its open space. The emphasis changed directly to the hill summit rather than the summit and slopes. With the contraction of the defences more tightly to the linear boundary formed by the cliff, the site was more or less transformed from a hillfort to cliff-edge fort. However, Cotter (ibid., vol. 2, 280-81) also noted that, following the refurbishment works, the form of the inner enclosure took on the appearance of a central citadel and that it had very clear affinities with high-status cashels and other prestigious western stone forts, such as Dún Eochla (GA110-138----), also on Inis Mór, and Dún Chonchúir (GA119-054----), Inis Meáin, and Cahercommaun (CL010-064003-) in county Clare, as well as a small number of well-defended promontory forts, such as Dunbeg (KE052-270001-), county Kerry. Subsequent modifications and alterations to the walls since the remodelling have resulted in the fort as it survives today and include the five buttresses built against the external wall-face of the inner enclosure during conservation works in the 19th century. It is likely that the material for the buttresses came from the quarry ditch running between the middle enclosure wall 2b and wall 3 (ibid., vol. 1, 226). During the course of the research excavations between 1992 and 1995, Cotter (ibid., vol. 1, 69-71) established that human acti