Sprawling Raby Castle was a stronghold of the Catholic Neville family until it engaged in ill-judged plotting (the 'Rising of the North') against the Protestant Queen Elizabeth in 1569. Most of the interior dates from the 18th and 19th centuries, but the exterior remains true to the original design, built around a courtyard and surrounded by a moat. It's 6.8 miles northeast of Barnard Castle; take bus 85A (£3.10, 15 minutes, eight daily Monday to Friday, six Saturday and Sunday).
The stables now house tearooms. There are beautiful formal gardens and a deer park; you can hire bikes to explore them.