 Dolbadarn Castle is a fortification built by the Welsh prince Llywelyn the Great during the early 13th century , at the base of the Llanberis Pass , in North Wales . The castle was important both militarily and as a symbol of Llywelyn 's power and authority . The castle features a large stone keep , which historian Richard Avent considers " the finest surviving example of a Welsh round tower " . In 1284 Dolbadarn was taken by Edward I , who removed some of its timbers to build his new castle at Caernarfon . The castle was used as a manor house for some years , before falling into ruin . In the 18th and 19th century it was a popular destination for painters interested in Sublime and Picturesque landscapes . It is now owned by Cadw and managed as a tourist attraction , and is protected as a grade I listed building . 
