China’s Great Wall was first built in the 3rd century BC and for hundreds of years has been built up by successive leaders to defend against threats from nomadic tribes. But natural erosion the footsteps of millions of visitors have taken a toll on the globally recognised historical site which is crumbling in many areas. Professional photographer He Tao fell in love with the Great Wall as a subject in 2012, and has gone on to document dozens of points along the wall, which by some estimates…