On April 19th, the Annual Regional Assembly of the Regional Planning Association (RPA) of New York looked some what different. In the audience were representatives from 10 cities and World Bank staff. RPA was launching the 4th Regional Plan for the New York region, and other cities were there to listen, learn and bring their own experience to the table. Why metropolitan planning and why New York? What brought this group together and how does peer-to-peer learning bring a new dimension to the process of learning? How does it influence better outcomes and a rich iterative process of evidenced based learning? Let’s start at the very beginning.