Beaumaris is the last and most technically perfect of the ring of great castles built by Edward I of England to consolidate his Welsh conquests. Started in 1295, but never completed as fully designed, it enjoys World Heritage status. With its pleasing symmetry, water-filled moat, succession of four concentric 'walls within walls' and stout towers and gatehouse, it’s what every sandcastle maker unknowingly aspires to.
The overall effect may seem more fairy tale than horror story, but the massive gates with their murder holes (used to pour boiling oil on invaders) hint at its dark past. The walk along the top of part of the inner wall gives super views of the castle layout and the breathtaking scenery that surrounds it. Look out for the old privvies (drop toilets, marginally less unpleasant than the murder holes for those walking below) and the arrow slits in the wall for picking off unwelcome visitors.