With 7/10 of the population which will live in urban center by 2050, Cities face huge challenge inviting to rethink the very concept of a City. The Smart Cities concept proposes to use Information and Communication Technologies to design sustainable solutions for improving socio-ecological aspects of cities. In this paper, we present the challenge of designing IT applications in Smart Cities and present our own attempt to transform our university into a Smart Campus. Through examples of use cases, we discuss how the Smart Cities concept intends to put citizen back at the center of the city and highlights that inter-disciplinary work is mandatory to address the challenges of Smart Cities.