Craig-yr-Aderyn ('Birds Rock') hillfort is a dramatically situated stone walled fort that has produced finds of the Roman period. The hillfort is built upon the landward saddle of ground against the almost sheer towering outcrop of Craig yr Aderyn which reaches 233m above sea level and commands extensive views along the line of the Dysynni valley, to the coast to the west and to the peaks of Cadair Idris to the east. The highest blunt peak of the outcrop is unusable slope, but the 'col' or saddle to the south-east occupied by the fort comprises a series of terraces and more open plains suitable for occupation. Further to the south the ground rises again in two impressive rocky crags, characterised by frost-shattered screes, bare outcrops and conspicuous quartz seams. Atop the tallest peak here, attaining 258m, is a large Bronze Age cairn (NPRN 407753). The whole provides a dramatic setting for the hillfort.

The hillfort comprises two clear periods of enclosure, with a smaller upper fort (c.0.6ha) defined by a single rampart with fairly restricted space for settlement, and a lower and more complicated extension (enclosing a total of c.1.6ha) enclosing areas of more level ground and featuring a well-preserved and complex gateway.

The upper, inner fort measures about 100m x 55m and presumably represents the earliest phase of enclosure. Its ramparts, now turf covered, meet at an angle on an outcrop and fade away into the steeper slopes of the rock. A deep earthwork remains of its main gate on the east side which may have been a formal walled corridor beneath a crossing bridge. This upper fort has very little level ground and there is no identifiable traces of platforms.

The lower, larger enclosure measures approx. 119 x 170m, building upon and extending the earlier enclosure. Its defences comprise a main stone-built wall curving around to the east and continuing north to the cliff edge. Although now a tumbled mass of scree, remnants of wall-facing can be seen in places confirming the rampart was once a prestigious reveted wall. There is a fair amount of burnt stone within the rampart, no doubt arising from domestic activities within the fort. It is conceivable that the stone rampart may have been strengthened with timberwork but there is no evidence of this on site. This main inner rampart wall is augmented by a second line of defence, comprising an earthen terrace and outer ditch on the south-east and east sides to the east of the main gate, and a tumbled stone wall running west of the main gate.

The main gate is a sophisticated structure, built at a point which takes maximum advantage of a wall of outcropping rock to form the eastern flanks of the gateway passage. These outcrops are augmented, on the right hand side as one enters, by a curving earthen terrace and outer ditch below, with an outward curving stretch of the inner rampart above, forming in effect a defensive 'bastion' arrangement on the right hand side. From a distance this arrangement gives the appearance of tri-vallate defences flanking the gate. On the left as one enters, the defences are lower and less impressive. The sides of the 21m long entrance passage, originally stone-walled and reveted, narrow as one continues into the fort and end with a pronounced in-turn. Given the height of the surviving rampart wall, and the amount of tumbled stone which has infilled the passage, it is likely that this passage was originally completed with a crossing bridge between the rampart terminals at the inner end, supported on timber posts.

In the nineteenth century a 'cwt' or hut, within the fort was dug into. The finds included Roman pottery, a weight or plumb bob, of rolled sheet lead (illustrated by Wynne Ffoulkes) and part of a curved lead bar, possibly an armlet. Weathered trenches can be observed in the eastern angle of the outer enclosure. To the west of the main gate, rectangular structures or folds have been built from the stonework of the outer rampart at an unknown date. Given the proximity of Castell y Bere castle to the east, and the visibility of this towering outcrop in the regional landscape, it remains highly likely that parts of the hillfort were re-occupied in the early medieval period although there is no firm evidence of this.

RCAHMW field visit 7th November 2013.

Sources: Wynne Ffoulkes in Archaeologia Cambrensis 4th series V (1874), 315-6
Royal Commission on Ancient and Historic Monuments , 1921 , Merioneth
Bowen & Gresham 'History of Merioneth I' (1967), 142-4, 262, figs 56-7

Toby Driver, RCAHMW, 8th Nov 2013.