Before the English built the town of Conwy, Aberconwy Abbey, the site was occupied by a Cistercian monastery favoured by the Welsh princes,[3] as well as the location of one of the palaces (called llys) of the Welsh princes. From Conwy: "the oldest structure is part of the town walls, at the southern end of the east side. Here one wall and the tower of a llys [palace/court house] belonging to Llywelyn the Great and his grandson Llywelyn ap Gruffydd have been incorporated into the wall. Built on a rocky outcrop, with an apsidal tower, it is a classic, native, Welsh build and stands out from the rest of the town walls, due to the presence of four window openings. It dates from the early 13th century and is the most complete remnant of any of his Llys."
The location also controlled an important crossing point over the River Conwy between the coastal and inland areas of North Wales, that Deganwy Castle for many years had defended.