Dolbadarn Castle was built between 1220AD and 1240AD by Llywelyn the Great. At this time, the Normans had begun advancing into north Wales, and fortifications were considered necessary in order to deter further encroachment. Placed strategically at the foot of the Llanberis Pass, Dolbadarn presented a significant obstacle to any army attempting an incursion into Gwynedd.

Dolbadarn Castle's usefulness was short-lived, however. In 1283AD, it was seized by the English under the command of the Earl of Pembroke. Two years later, the castle was plundered for its stone and timber, then subsequently abandoned.

Although no longer useful as a fortification, Dolbadarn's remaining buildings were put to use as a domestic manor house up until the 14th Century. After this time, the entire site fell into decay, and by the 18th Century it was entirely ruinous.

Today, the site is dominated by its round tower, the remains of which are 40ft high and 40ft in diameter. Of the other buildings, only the foundations remain. The round tower occupied a south-eastern section of the curtain wall, while two rectangular towers guarded the vulnerable western slope and the castle entrance. The north of the castle is occupied by a building thought to be an addition made by the English during their brief occupancy, which is likely to have served as a hall. A final building occupied the eastern wall, but its function is unclear.

Although small in stature, Dolbadarn Castle occupies a stunning spot, sitting atop a rocky crag overlooking the Llanberis Pass and the waters of Llyn Peris. The views are absolutely stunning, and seen from a distance, the castle presents a striking picture when bathed in the late evening sun.