Cities spend an aggregate of 10% of world GDP annually on procurement of services to improve the lives of billions. Yet, at systemic level the process is flawed by discouraging the discovery of innovations and shareable solutions to urgent needs, instead often encouraging re-invention. Citymart and the #citiesshare alliance are promoting an approach where cities open their problems and procure by challenge to enable the global marketplace of social and urban innovators to inspire better choices. Procuring by problems enables cities to become more open to innovation and transparent about their decision processes. Procuring by problems enables cities to become more agile and responsive to the needs of their citizens, rapidly connecting to the best available solutions. Procuring by problems finally helps cities improve their understanding of risk, away from the uncertainties of working with 'unknown' providers and towards a more emphatic approach to delivering improvements for their citizens. Welcome to Citymart: Inspiring solutions to transform cities.