Four strange places to see London's Roman Wall

On the subject of walls... Cortez reported seeing a wall blocking off an entire valley on his way to Tenochtitlan. One source reported the wall was 6 miles long, and yet it seems to have disappeared without a trace. And yet, Both the London Wall and Hadrian's Wall, though much older still have surviving ruins to this day.

I wonder if they exaggerated things to make their conquest seem even more impressive