Milan's Bosco Verticale features two residential towers covered in 20,000 plants that act as a natural air conditioning system.

Designed by Boeri Studio and inaugurated in October 2014, the Bosco Verticale consists of two towers standing 111 meters and 76 meters tall in Milan's Porta Nuova district. The project was a massive botanical experiment led by architect Stefano Boeri and a team of botanists who spent three years selecting the right plant species. They chose 800 trees, 4,500 shrubs, and 15,000 floral plants based on their resistance to wind and sun exposure at different heights.The environmental impact is measurable and significant. The vegetation absorbs approximately 30,000 kilograms of carbon dioxide and 19,000 kilograms of dust particles every year. This biological shield regulates humidity and produces oxygen, effectively reducing the internal temperature of the apartments by up to 3 degrees Celsius during hot Italian summers. This natural insulation significantly lowers the energy consumption required for mechanical cooling systems.Beyond climate control, the towers serve as a 'spontaneous recolonization' site for urban biodiversity. Since their completion, researchers have documented over 1,600 specimens of birds and butterflies nesting within the facades. The maintenance is performed by a specialized team of arborists known as 'Flying Gardeners' who descend from the roof using mountaineering equipment. This innovative approach to urban forestry has since been replicated in cities like Nanjing and Utrecht.