Opened in 2014 and called "the most exciting new tower in the world," Milan's Bosco Verticale, or "vertical forest" comprises two 27-story residential high-rises teeming with cantilevered balconies and planted with almost 900 trees and more than 2,000 shrubs and bushes. 

The project was proposed by architect Stefano Boeri as part of his BioMilano: six ideas for a bio-diverse metropolis. His firm describes the towers as "a model for a sustainable residential building, a project for metropolitan reforestation that contributes to the regeneration of the environment and urban biodiversity."

Bosco Verticale's extensive greenery provides apartment dwellers with shade in the summer and filtered sunlight in the winter, as well as cleaner air and reduced noise pollution. The buildings are also equipped with solar panels and a gray water recycling and irrigation system.