Bosco Verticale, Milan

Stefano Boeri's Bosco Verticale (Vertical Forest) in Milan, completed in 2014, comprises two residential towers hosting 800 trees, 4,500 shrubs, and 15,000 plants — the equivalent of 30,000 square metres of urban forest on a 1,500 square metre footprint. The trees provide insulation, reduce noise pollution, absorb CO2, and create microhabitats for birds. It won the International Highrise Award and inspired dozens of imitations worldwide.