The mobile phone is widespread all over the world. This technology is one of the most widespread with more than five billion subscriptions making people describe this interaction system as Wireless Intelligence. Mobile phone networks become the focus of attention of researchers, organizations and governments due to its penetration in all life fields. Analyzing mobile phone traces allows describing human mobility with accuracy as never done before. The main objective in this contribution is to represent the people density in specific regions at specific duration of time according to raw data (mobile phone traces). This type of spatio-temporal data named CDR (Call Data Records), which have properties of the time and spatial indications for the elaborated environment. City life understandings help urban planners, decision makers, and scientists of different fields to resolve their questions about human mobility. Such studies are using a very cheap, most spread tool that is the mobile phone. Mobile phone traces analysis gives conceptual views about human density, connections and mobility patterns. In this study, the mobile phone traces concern an ephemeral event called Armada, where important densities of people are observed during 12 days in the French city of Rouen. To better understand how people attracted by this event, city area during these days of this ephemeral event, is used. Armada mobile phone database is analyzed using a computing platform integrating various applications for huge database management, visualization and analysis, in order to explore the urban pulse generated by this event. As result, city pulsation and life patterns are explored and visualized for specified regions.