It seems kind of strange that the first World Heritage Site in Wales should be a symbol of subjugation by the English, but that's what the Castles and Town Walls of King Edward I in Gwynedd, a former principality in northwest Wales, represent. I thoroughly enjoyed my visit to three of the four inscribed castles over two days in the spring of 2005, so I suppose I should thank the Welsh for their independent nature which led King Edward I to construct these fortresses. From my base in Betws-y-Coed, I first made my way to Conwy, where a 13th century castle sits above the wall-enclosed town. The views of the countryside and town from the walls were spectacular, and I enjoyed exploring the castle. Beaumaris, on the nearby island of Anglesey, was slightly less impressive, though I did appreciate its symmetry. My last stop was to Caernarfon, where the outgoing tide left a row of boats stranded in the harbor below the town's imposing fortress. This castle is perhaps best known for serving as the site for the investiture of the Prince of Wales, and it may once again receive the spotlight when the ceremony is next held. I've seen many European castles since this trip, which has perhaps influenced my recollections, but even if these aren't the most spectacular castles I have ever seen, I found these to be well worth a visit.
Logistics: Some of the castles of northwest Wales are accessible by various means of public transport, as mentioned below; I found it quicker to navigate via a rental car. Incidentally, if visiting Conwy, I highly recommend a stop to nearby Bodnant Garden, which is spectacular in the spring.