By the end of 2012, a hectare of trees will have been planted in the central city of Milan in Italy – on the sides of a building. The world’s first ‘vertical forest’ is under construction and, when it is complete, the twin towers of the development will stand 27 floors high, and be home to 730 trees, 5000 shrubs and 11,000 ground plants. It will be known as the ‘Bosco Verticale’, and its designers envisage that it will act as a filter for pollution, attract birds and wildlife, and provide shade on hot summer days. Apartments in the building will range from $1.1million for a low-level, 80 square-metre apartment to $3.2million for a 200-square-metre penthouse suite with views over the city (between the trees). Tree varieties have been tested with wind turbines, so that only varieties strong enough to resist high winds have been selected. The towers are the brainchild of world renowned Milan architect, 55-year-old Stefano Boeri.