Caerphilly Castle is the largest medieval fortress in Wales and Britain's second-largest castle, a monumental achievement built primarily between 1268 and 1271 by Gilbert de Clare to control Glamorgan and defend against Welsh territorial ambitions. The fortress covers 30 acres and pioneered concentric defensive architecture with inner and middle curtain walls, four corner turrets, and sprawling water defenses. Notably, its famous leaning tower has tilted three meters out of perpendicular since 1648—even Oliver Cromwell's forces could not breach its boundaries, leaving only a remarkable scar on this impressive medieval stronghold.
