This is the first part of a three-part commentary addressing the three challenges of the title, which also were the main elements of the Kuching statement on Healthy Cities, which focused on People, Planet and Participation. In this part, my focus is on the roots of these ideas for me, the question of what business cities should be in, and on people in terms of social justice, social inclusion and health equity. The second part will focus on ecological sustainability and health, the third on healthy urban governance and a new initiative I am pursuing, Conversations for a One Planet Region. A shorter version of these three pieces will be published on the CityMinded blog.