It is unique in the Roman World. A spectacular and complex stone barrier measuring 74 miles long, and up to 15 feet high and 10 feet thick. For 300 years Hadrian's Wall stood as the Roman Empire's most imposing frontier and one of the unsung wonders of the ancient world.Almost 2,000 years after it was built, Hadrian's Wall is proving to be a magical time capsule - a window into the human past. Archaeologists have properly excavated less than 1per cent of it, but they have unearthed extraordinary findings. With presenter Julian Richards Timewatch journeys back through time to unlock the secrets of a lost world.