With its cone whitened by the eternal snow, the Cotopaxi is one of the postcard landscape in Ecuador. Yet the volcanologists claim it is a threat. Indeed, an eruption would lead to a mudslide that would deprive the inhabitants of Quito of running water. It is not an isolated case in the country because over 25 volcanos active or very active constitute “the volcanos boulevard”. Located on a seismic fault Quito is permanently threatened by an earthquake. But if theses natural risks are unavoidable, some disasters could be prevented.