Recognizing the importance of the services provided by forests and trees to urban dwellers, the Collaborative Partnership on Forests proposed that the theme for the 2018 International Day of Forests would be "Forests and Sustainable Cities". To mark this occasion and promote the widespread adoption of "green" strategies for dealing with urban challenges, FAO invited the mayors of 15 different-sized cities from various regions around the world to present their experiences with trees and forests and to show how this green infrastructure has helped address urban challenges. Though this overview is far from exhaustive, the stories presented show that investing in green solutions can pay dividends, while increasing the resilience and liveability of urban environments.