The contemporary urban evolutions reduce the role of the center by dissociating it from the concept of gathering. This threat of an empty center questions the town planner for whom space exists only by his frequentation. By supporting us on a fieldwork in Bobigny. Créteil and Nanterre, we arc interested in the " city like gathering (H. Lefebvre), then with the "practice of the gatherings " (E. Goffman). The ethnographic work undertaken within groups of young people indicates the relative and "located" character of the urbanity of the uncountered situations. Given the tests which they have to face at the time of their daily movements. The young people set up modes of appropriation, anticipation, territorialisation and passage which are as much of "territorial cultures" neglected by urban policies. Intentionally causing a legitimate concern among the various urban actors, the "public pauses" eau contribute to the realization of a practical public space.
