I was walking through Filey last week with GS (9), and he was telling me about Hadrian's Wall (not sure how the conversation came about). "It's the longest wall in the world, Nanny" he said. I told him no, the Great Wall of China is the longest. No it can't be, came the reply, because it's a hundred kilometres long, and that's very long! Well, I told him that the GWofC was thirteen thousand miles long (I don't do kilometres) and it could be seen from space! By this time, he is getting a bit frustrated at being contradictedy some old woman who doesn't go to school anymore so can't know anyone, and he turned to me with his hands on his hips and said in a very terse voice, "yes but it didn't keep out the Picts did it!" I couldn't contradict that one! When we got home, I showed him pictures of the GWofC and he had to admit it was just a bit more impressive than Hadrian's Wall.