The remains of the castle include a round tower and stone walls. Castell Dolbadarn is a thirteenth century castle built by Llywelyn ap Iorwerth (c 1172- 11 April 1240). Known as Llywelyn Fawr (Llywelyn the Great) by the end of his reign he had become the most powerful of the Welsh rulers. Dolbarden was built in about 1220 and is located above the lake of Llŷn Padarn in the Llanberis Pass (Welsh: Bwlch Llanberis) in a very strategically important position. The dominating feature of the castle is the forty foot high and forty foot diameter tower with walls of some eight feet thick. The castle continued in use after the death of Llywelyn Fawr and is thought to be the place where Llywelyn’s grandson, Llywelyn ap Gruffudd imprisoned his own brother Owain ap Gruffudd, who he saw as a threat to his power, for some forty years. The castle lost its strategic importance from the beginning of the fourteenth century and gradually fell into ruin.
This is a magnificent site to visit as you enter the Pass of Llanberis on the edge of Snowdonia National Park with stunning views over Llŷn Padarn. It is located behind the Royal Victoria Hotel in the village of Llanberis which lies on the southern banks of the lake. It can be reached via a footpath from the A4086. This is a site that is really well worth visiting with its dark brooding tower continuing to standing guard over Llŷn Padarn.