In 1977, the artist David Nash planted 22 ash saplings in a ring. A decade before, he had come to north Wales and made his home in a former mining town. He was drawn to working with wood—it’s still his primary medium—but Ash Dome was his first work that involved planting.

He arranged the trees in a circle and, as they grew, he used techniques from British hedge-making practices to bend the trees into a unique gathering. “Part of the point about Ash Dome was: Hands On!” he told Sculpture magazine, in contrast to the sense that humans should not interfere with nature.

Ash Dome was always intended to be a long-lived work; Nash planted it in the region where he lived so that he could stay with it over time. He sometimes describes it as a space for the 21st century, and he told Sculpture magazine that he and his wife were there when the last millennium turned to this one. Forty years on from its planting, the dome is still growing.