Powis Castle in Powys

You're standing at Powis Castle, just outside Welshpool in Wales. It started life as a medieval fortress and slowly grew into a grand country house. And here's the twist: it was built by a Welsh prince, Gruffydd ap Gwenwynwyn. Most castles along this border were put up by the English or by Norman barons to keep the Welsh in check. Parts of the stonework still date from the thirteenth century.