4. Caer Seion, Conwy Mountain

SH 760 778

The features marked with letters in red are described below but the other features on the plan can also be recognised although some are slight or hidden by heather. The track marked on the plan is the North Wales Path from which a small path leads up the slope at the south side of the hill. The North Wales Path can be joined either from Mountain Road, Conwy, at the east, or from the small car park at Pensychnant Pass at the west, both about 25mins walk.

Caer Seion is a large and strong hill fort. Excavations were carried out in 1951 but did not produce any dating evidence. However, it is believed to have been occupied during the Middle to Late Iron Age, about 300 BC to 1st century AD and it seemed likely that the fort was abandoned when the Romans conquered North Wales in 78 AD. The fort had a commanding position overlooking Conwy Bay and estuary and over the ancient trackway that followed the coastal ridge, continuing westwards towards Anglesey. The next nearest strong forts and possibly tribal centres are at Pen-y-dinas on the Great Orme, Pen-y-gaer above Llanbedrycennin and Braich y Dinas above Penmaenmawr.

The fort had two periods of defence. In the first period a single stone wall of 3 to 4m width encircled the whole hill top apart from at the steep north side where no defence was needed. It had one entrance (A), at the south side, which would have had a timber gate. The greater width of the wall around the gate suggests it had a ‘fighting tower’ over it. Within the fort were over 50 timber round houses, many just behind the rampart at the south side (to shelter from the wind) and they are visible as circular platforms terraced into the hill slope (B). They varied in size from about 4m to 8m diameter and traces of walling survive at some of them. In one place there is a possible corn-drying kiln (C).

In the second period a smaller and stronger fort was constructed at the west end of the hill. The older fort appears to have still been occupied but there was no access between the two. The smaller fort had somewhat wider walls and a strong gateway protected by bastions on either side (D) and probably a ‘fighting tower’. Comparison with similar forts suggests that the wall would have been about 3 to 4m high with a walkway and breastwork wall on top. The defences were further reinforced by the addition of deep ditches at the east, north-east, west and south-west (E). The entrance was also protected by an ‘outwork’ (F) – an outer wall that made rapid, approach to the entrance impossible and exposed any attackers to missiles from the defenders on the overlooking inner walls. The entrance through this outwork was later blocked (G).

The excavations carried out in 1951 found a hearth inside one house in the small fort as well as spindle whorls (for spinning wool) and a quern (for grinding corn). In the large fort the house next to the entrance contained over 400 sling stones, so perhaps was a ‘guard chamber’. It may be that the small fort was built during the period between the first Roman attack on north Wales in 60AD and the final conquest in 78 AD. The absence of Roman period finds from the fort suggested that it was not occupied after the Roman conquest, and so it may have been destroyed and deserted. However, there is a tradition linking the fort with Maelgwn Gwynedd in the 6th century and it has been suggested that the small fort belongs to that period.

Outside the fort are some remains of stone-walled roundhouses that may have been occupied at the same time as the fort or during the Roman period. One (H) lies in a slight level hollow at the north side of the North Wales Path just east of the path up to the fort. It consists of one large roundhouse and probably several other smaller buildings. The other (J) lies on a terrace on the slope below the south-east angle of the fort and consists of just a single large roundhouse.


The fort and area around it are protected as a Scheduled Ancient Monument in the care of Cadw. Any kind of damage, digging or metal detecting is prohibited. The fort lies within the Snowdonia National Park and the area of the fort and the paths are cared for by Conwy County Council. Please report any problems or damage.

Conwy County Council, Countryside Section: 01492-575200
Snowdonia National Park: 01766-770274
Cadw: 01443-336000
Gwynedd Archaeological Trust: 01248-352535. Web: www.heneb.co.uk