At work in the Coventry Garden, the Japanese concept of mu, the "expression of emptiness". It provides space for reflection. At the instruction of the school children, meanwhile, a bridge was placed between the larger stones to symbolize the unity of people. Another concept is shakkei, the "borrowed landscape" – the trees, for example, outside the garden, but still part of its perspective. "It is widely used in Japan," says Hardman, "to give the garden a broader context." Although something is undesirable, an old barn or a neglected parking lot is immediately screened off. Gardens designed by JGS include one on the roof of London's Great Ormond Street Children's Hospital. It is maintained by the society's volunteers, and is well used by staff, who find their holiday there as 'restorative', says Hardman. Parents find it 'very useful for them as a place to look at another scene, given the disturbing feelings of their children ill'.