An urban forest is growing in Milan, Italy.

Bosco Verticale is a pair of residential apartment towers that are being constructed in the centre of the city. Upon completion later this year, the Stefano Boeri-designed buildings will be the world’s first vertical forest.

The “green” highrise complex, which consists of two 285-feet (18 floors) and 290-feet (26 floors) high structures, will feature massive reinforced concrete balconies with lush trees and shrubs. A total of 120 large and 544 medium-sized trees, and more than 4,000 shrubs and bushes will be planted on the façade from top to bottom. On flat land, each “vertical forest” is the equivalent, in amount of trees, to 10,000 square metres of forest.

The vegetation will take on the important functions of a forest: reducing carbon dioxide levels while simultaneously producing oxygen. The planted areas will also provide residents with protection against noise and dust. In summer, the treetops will shade the apartment units against direct sunlight; in winter, they will allow the rays from the low-lying sun through, thereby regulating the climate during all seasons. A reduction in humidity and effective wind protection is also expected.

A model of vertical densification of nature within a city, the ambitious project broke ground in late 2009. It was designed as part of the environmental rehabilitation of Milan – one of the most polluted cities in the world.