Llys Dinorwig comprises two parts: (i) the foundations of at least one rectangular building within an enclosure defined on the west, south and east sides by a fortified scarp and ditch. (ii) to the north of the enclosure is a single length of wall, 45ft long, 3ft 3ins wide and 17ft high, representing a further building of possible medieval date. The site was known to Pennant and Fenton and the reference by Leyland to Sir Gruffydd Llwyd as the 'Lord of fair Dinorwig' is significant.
Sources: Cadw scheduling description and RCAHMW Caernarvonshire Inventory, Volume II No. 1153