There is a link between phenomena covered by the umbrella term «urban mobility» and the wealth of social and spatial dynamics active in de-structuring the city as a coherent spatial model, a process known as «urban fragmentation». It is therefore reasonable to hypothesise that the combination of urban mobility and urban fragmentation has a decisive impact on the formal and spatial evolution of contemporary cities. In order to investigate the spatial changes underway, we have selected public space as a study area. As a result of intense research interest over the past 20 to 30 years throughout the world, public spaces are now considered to be the most important areas for the creation of the city, be it spatially or socially. The evolution of the concept of public space has been considerable. Most researchers today agree that it is not simply a set of pavements, parks and town squares: social dynamics also form an integral part of public space. This is why it is important to understand public space as an essential component of the city, which is able to constantly adapt its shape or size. These changes can induce spatial fragmentation which in turn causes social segregation in the city (power inequalities, access inequities, etc.). The interest of our research lies therefore in the analysis of the relationships between urban fragmentation and urban mobility, from the vantage point of public space. In order to give a practical grounding to our work, we analysed several public spaces, with a view to understanding the processes leading to the creation and development of public space. This research was carried out in Bogotà, the capital city of Colombia, because the great cities of Latin America are confronted - perhaps more than other cities elsewhere - to a rapid socio-spatial fragmentation process. In view of this risk, some cities have undertaken major urban restructuring campaigns with almost military undertones, within which public spaces are viewed as prize assets. This is the case of Bogotà, a prime location for observing both urban fragmentation and creative reactions against it: spatially through the study of public spaces, and socially through the analysis of public and private mobility practices.