Dinefwr, near Llandeilo, has been a seat of power since Roman times: the 12th-century castle was the court of Lord Rhys, Prince of Deheubarth, whose descendants lived at Newton House for over 300 years. The 17th-century house is now a mix of period rooms, exhibitions and dressing-up, set in 800 acres of 18th-century parkland laid out by George and Cecil Rice, now a National Nature Reserve with veteran trees, an ancient fallow deer herd and rare White Park cattle. The parkland and the castle, cared for by Cadw, are free to walk, though parking is charged; the Oak Yard has water play for children, and dogs on leads are welcome on the ground floor of the house but not in the Deer Park. Reviewers single out the basement cinema, the cafe flapjacks and the hour-long loop up to the castle. Tips from regulars: ignore the sat nav, follow the brown signs, and download the JustPark app before setting off.
