Caerphilly has the distinction of being the largest castle in Wales (and the second largest in Britain) so you certainly get your money’s worth when you visit (particularly when the chap in the ticket office sees your grey hair and charges you the cheaper senior admission price even though you’re not actually that old!) (I am no longer insulted by such things, preferring instead to enjoy the benefits my aging brings!).
The Castle dominates the town but not in the way you would normally expect from a castle. It isn’t sited menacingly on a lofty hillock; instead it sits in a natural bowl surrounded by water, like a gigantic plug in a basin of water. I always expect castles to sit where they can defend access to a territory and forget that many were built to protect their people from attacking armies, which Caerphilly is certainly well equipped to do. (You can read more about why Caerphilly is a masterpiece of military architecture here.)
This castle is a truly impressive location to explore, with narrow winding stairways, guardrooms and grand halls, battlement walkways, a dramatic leaning tower, panoramic views, working examples of trebuchets, the ruins of a mill, huge wooden doors, and, sometimes, if you’re really lucky and your timing is right, there’s even a dragon! (My timing was wrong but I will be going back again soon!)