This document summarizes the Apps4Warsaw project which involved multiple partners including 3 NGOs, a public technical university, a major telecom company, and the city of Warsaw. The project aimed to build an open data platform and engage the community. Over an 11 month period, the partners built a scalable platform with selected city data sets and an API. A competition and incubation process was then launched which engaged over 30,000 people and resulted in 50 data sets, 71 project submissions, 20 finalists, and 4 working apps being developed.