Picton Castle, Haverfordwest, Pembrokeshire, Wales.
Picton Castle is a most unusual ancient building being as it is a fully developed medieval castle that was transformed into a stately home in the 18th century.
From the outside with its four symmetrically spaced half round towers and gatehouse entrance flanked by two narrower towers it is based upon patterns of Irish castles of the period and is the only one of this type in the mainland UK. As soon as one enters inside it is revealed not to have an inner courtyard and keep but rather a series of finely planned rooms typical of the grand country house that it is. There is no other building quite like it in Britain.