Cities are increasingly outfitted with sensors for monitoring various conditions such as traffic, weather, air quality, and infrastructure related issues. Such well outfitted cities are generating massive amounts of multi-modal data leading to daunting challenges in assimilating, visualizing, and making sense of this data by city authorities and citizens. We propose City360 to address these challenges and provide decision support to city authorities and citizens. We demonstrate the utility of our system through concrete use cases for San Francisco Bay area that utilize heterogeneous data from various open city data sources.