Could vertical forests improve our cities and health?
Bosco Verticale in Milan is a pair of residential towers with over 900 trees and 11,000 plants.
A UN 'World Cities' report, external has predicted that two thirds of us will live in cities by 2030. Could buildings like Bosco Verticale help to tackle pollution and improve people's health?
Digital producer: Jack Burgess Camerawork: Anand Jagatia
Discover more in CrowdScience from BBC World Service.