After Conwy Caernarfon is the most impressive of the Edwardian castles, and since Edward planned it as a palace for the Mrs it's no surprise. Since it used to be all white from the outside it must have been some sight when it was first built, too. The remaining ruins are also in rather good condition which leaves you with a lot to explore. Personally I was a bit vexed I'm dependant on my phone's internet connection for geocaching, because that place clearly begs to be used for caching (or playing hide and seek, but Crocky wasn't up for it).