Posted by Phoneblog at 9:48 PM Sunday, February 13, 2011 Caernarfon Castle. Caernarfon Castle  ( Welsh :  Castell Caernarfon ) is a medieval building in  Gwynedd , north-west  Wales . There was a  motte-and-bailey  castle in the town of  Caernarfon from the late 11th century until 1283 when King  Edward I