Walking tour on the Great Wall

A excursion to the Great Wall of China, destination of almost all tourists who explore Beijing and the surrounding area. Thousands of tourists stumbled up and down. It is exhausting to walk a few kilometers on the wall, because it is always steep up and down and just a little straight ahead.
The wall was 8.851.8 km long, when it was surveyed by Chinese authorities in April 2008. I heard about 6,200 km a Swiss and a US citizen managed to hike along the wall, they took several years.