Cities are becoming big generators of data. In the past, decision makers of cities had to make educated guesses about their cities based on small data sets or even just their gut feel. Today, it has become possible to listen to a city’s heartbeat in the massive amounts of data that it generates—from sensors monitoring smart buildings and the environment, to positioning systems navigating moving vehicles, to netizens tweeting about the city in the social media, all in real-time. The data are no longer just accessible by the policymakers but they are also increasingly made available to the business operators and citizens of the city. This new abundance of urban data can be a game-changer for building better cities, if we can make the data work for the city using intelligent and scalable data analytics. In this paper, we will describe A*DAX, a data analytics platform for smart cities to harness the power of big data in the city into new urban solutions for the city.