The Ming dynasty built a giant wall stretching 5,000 miles to keep invaders out of China, but how effective was it against the enemy?

This is from a short canoe trip last fall. Alot of things came together to make this shot--timing, planning and scouting. I knew from the weather forecast that it would be cold (-2 C) and that meant that mist would form. I had scouted out the location the evening before. I got up before dawn, made coffee for my wife ( the paddler ) and convinced her of the beauties of the early morning.