Welsh castle and solitary guardian of Snowdonia’s Llanberis Pass
Occupying a lofty, lonely spot overlooking the waters of Llyn Padarn, native-built Dolbadarn Castle was once a vital link in the defences of the ancient kingdom of Gwynedd. Most likely constructed by Llywelyn ap Iorwerth (Llywelyn the Great) in the late 12th or early 13th century, it stood to watch over the strategic route inland from Caernarfon to the upper Conwy Valley.
Today the site is dominated by the sturdy round tower, very different in style to the unmortared slate slabs which make up the castle’s curtain walls. Standing 50ft/15.2m high, the tower’s design was probably inspired by that of similar fortresses built by Llywelyn’s rivals in the borderlands of the Southern Marches.
https://cadw.gov.wales/visit/places-to-visit/dolbadarn-castle