One of the things British sculptor David Nash is known for is shaping living trees. His "Ash Dome," a ring of trees he planted in 1977, is made up of 22 ash saplings, which he pruned and shaped over decades to slowly bring the branches together to form a swirling cupola. "Ash Dome" emphasized a long-term, hands-on relationship to environmental stewardship. "Part of the point was that nature actually gets on very well when a human being is caring for it and lives with it," Nash says. The location of "Ash Dome" remains a secret, and whenever it's filmed, crews are taken to it by a circuitous route in order to guard its whereabouts. 

See the Ash Dome video here.