The public space in Latin American cities can be considered as a field of conflict, where many actors meet with their separate interests reflecting also structural city problems. Studies to date show different tendencies of utilization of public space: insidious privatization, spaces reduced to functional aspects, fields either for freedom or for control, or also for the demonstration of power or resistance. The interpretation as an instrument for the realization of transversal politics is of very recent date. With special reference to Cartagena (Columbia) and Quito (Ecuador) developmental tendencies are discussed. Both cities belong to the UNESCO programme 'Cultural Human Heritage', both have a well preserved colonial centre, a historically grown centrality and therefore principally an excellent starting situation for elaborating a novel perspective of urban development on the basis of 'public space'. This is a challenge for the municipal administration to create new opportunities for interaction. This process has been far advanced in Quito from 2009 to 2014. With the culture programmes, the communal bicycle project, and measures for the advancement of public safety a noticeable level of spatial coherence was created which represents the basis for the development of an urban relationship capital. With this concept of public space that was part of five of seven development axes of the Metropolitan plan's and of the colonial centre as well as of all sector plans a novel structure of spatial planning has been developed, a kind of supplementary co-ordination instrument at the micro level of spatial urban planning. In Cartagena such a process cannot be observed. The aims of the metropolitan development plans have been formulated clearly less accurately pertaining only to specific sectors. Elements of management and control dominate. Furthermore the development of the colonial centre has been a more or less isolated area of planning. There has been no specific policy for dealing with public space. With respect to the four urban development axes the colonial centre and public space have been mentioned only indirectly.