The Bosco Verticale, or Vertical Forest, high-rise complex stands tall in the modern district of Porta Nuova in Milan.
Italian architect and urban planner Stefano Boeri's creation, completed in 2014, consists of two skyscrapers containing more than 800 trees.
The symbol of green urban living is also covered in 15,000 plants which help absorb carbon dioxide and improve air quality. The buildings use renewable energy from solar panels and filtered waste water to sustain the plants.
According to Mr Boeri, Bosco Verticale was inspired by Italian author Italo Calvino's 1957 novel Il Barone Rampante, or The Baron In The Trees, in which the protagonist decides to abandon the ground and live in trees for the rest of his life.