11. Five Thousand Tons of Stone - Hamsterley, County Durham

The Time Team travel to County Durham to investigate the origins of a mysterious large stone structure which has had locals baffled for centuries. The stone structure is known locally as The Castles, its five-metre thick walls enclose a space the size of a football pitch.With guesses ranging from an Iron Age farm to a Roman prison, Tony Robinson and the team attempt to come up with a definitive answer.