David Nash, an artist, owns land in rural northern Wales. In 1977, he began growing and shaping a circle of trees to form this structure. It's a living sculpture of 22 ash trees called Ash Dome.
1977 was a dark time. The Cold War threatened to turn hot. The British economy was in shambles. There was widespread environmental apocalypticism. The overall mood was one of pessimism. The world seemed dead or in dire threat of dying. So Nash made this living work of art as a reaction to these challenges. You can see more photos of it and a BBC video at Colossal.