"I've attended a huge number of conferences of mayors and city leaders from across the globe. What's very interesting is that their concerns are nearly always the same," said Erik Solheim, former UN under-secretary-general and former executive director of the UN Environment Programme, referring to transport, parks, garbage and housing, among others. Drawing on years of conversations with city leaders worldwide, he made a simple but often overlooked point: What makes a city good isn't skyscrapers; it's planning and placing people's needs at the center.