 He built a number of castles to defend his borders, most thought to have been built between 1220 and 1230.These were the first sophisticated stone castles in Wales; his castles at Criccieth, Deganwy, Dolbadarn, Dolwyddelan and Castell y Bere are among the best examples.Llywelyn also appears to have fostered the development of quasi-urban settlements in Gwynedd to act as centres of trade.