The fortifications on Mount Yr Eifl were built around 200 BC. However, the largest number of people lived in the settlement between 150 and 400 AD, practically throughout the Roman period. Since Tre’r Ceiri was situated high above sea level (485 meters above sea level), it may have served as a refuge for summer shepherds who also had winter dwellings in the lowlands. The settlement was abandoned in the 5th century AD.
The settlement was erected on a hill elongated in plan, 485 meters high. It was surrounded by a perimeter of stone walls along the edges of the slopes, with a shape similar to an extended oval measuring 289 by 103 meters. The length of the defensive walls was about 620 meters. In addition, on the north and west sides, where the slope of the hill was the mildest, a second, outer wall was erected.
The thickness of the main wall ranged from 2.1 to 4.6 meters on the north-west side and from 1.8 to 3 meters in the safer southern and eastern sections. The height of the fortifications in some places is now less than 4 meters (from the outside, only 1.8 meters from the inside), with the parapet taking up about half the wall thickness and rising to about 0.9 meters high (originally it was certainly slightly higher). The entrance to the wall-walk was carried out by means of inclined ramps attached to the curtains. An experimental maintenance program has shown that the masonry was built by placing flat stones without careful selection for fit or facing. This meant that the wall could be built fairly quickly. Reconstruction work has shown that three men could build about 1 meter of wall per day. Surprisingly, the entire circuit could be completed by 100 workers in approximately 20 days.
The outer wall, apart from an obstacle directed against potential attackers, was a revetment against the slopes of the hill. Unlike the main wall, it did not have a parapet, although in places the top of the fortifications slopes so that it formed a depression with the hillside. Built of large, polygonal blocks of stones from the slopes of the hill, it was probably a later, secondary addition to the main fortifications of the settlement.
The entrance to the settlement was provided by two main gates and three smaller posterns in the form of ordinary gaps in the wall, about 0.9 meters wide. One of them was placed in such a place as to allow the inhabitants to reach the water source by a narrow path. The main gates were on the south-west and north-west sides, the latter referring to the gate of the outer wall, behind which the path turned sharply. The south-west gate was a 1.8-meter-wide break in the wall, preceded by external walls for a distance of about 15 meters, usually with the function of strengthening the slopes of the hill. On the inside, the gate passage was 5.5 meters long, flanked by a wall that was formed in the form of two semicircular bastions.
The area of the hill covered by the fortifications was sloping gently from the south-west to the north-east, until in the eastern part it reached the highest elevation of the Yr Eifl, surrounded by a defensive wall. There was a stone mound (cairn) with a diameter of about 15 meters, built of carefully placed but unworked stones. Within the walls of the settlement, there were also at least 150 smaller and 26 larger stone huts. They had round forms, horseshoe shapes with the backs joined together, and free-standing horseshoe shapes. There were also oval, polygonal and quadrilateral houses. The round ones had diameters from 2.4 to less than 8 meters, but were usually in the range of 3.6 – 4.6 meters. The elongated houses varied greatly in size, usually they were erected 2.1 to 2.7 meters wide and twice as long. All of them were built of local stones, with floors slightly below the ground level, probably originally with wooden roof trusses covered with grass. In Roman times, the settlement could accommodate up to 400 people. Other families could live at the foot of the hill, in houses fenced with stone walls with rounded corners.
Tre’r Ceiri (translated as “The Town of Giants”) is one of the best preserved defensive settlements from the Iron Age in Great Britain. To this day, a defensive wall has been preserved, visible on a large part of the perimeter, reaching up to 3.5-4 meters in height and the foundations of round houses. In 1989, Cyngor Dosfor Dwyfor and Gwynedd County Council, financed by the governmental agency Cadw, began under archaeological supervision a long program of consolidation and repair of the fort. The project lasted ten years and ended with the renewal of this valuable monument. Admission to its area is free.
The Royal Commission on The Ancient and Historical Monuments and Constructions in Wales and Monmouthshire. An Inventory of the Ancient and Historical Monuments in Caernarvonshire, volume II: central, the Cantref of Arfon and the Commote of Eifionydd, London 1960.
Website coflein.gov.uk, Tre’r Ceiri hillfort, Llanaelhaearn.
Website intarch.ac.uk, Tre’r Ceiri: An Exceptional Walled Fort.