Great urban events require the production of safe environments in which participants are able to partake in the event within a protected interior. In this paper we examine three different types of urban events : festivals, demonstrations and sports events. Police forces have become experts in the management of urban climates, relying not on plans but on the creation of conditions in which they themselves and the other actors function. While at the same time using all of their resources in order to maintain some control over the event and not be completely controlled by it.