More than rebuilding cities, planners are destroying them: this was the conclusión of The Death and Life of Great American Cities, a book published in 1961 by Jane Jacobs, then a cultural promoter married to an architect who through articles written for New York dailies made defending the city a true crusade. What Jacobs proposed, in opposition to Robert Moses and the social engineers close to the tabula rasa way of city building, was to preserve all that which gives value to cities: variety, density, and self-organization. Her ideas have now triumphed, in fact almost to the point of being dogma, and associations like the Municipal Art Society of New York commemorate the centenary of the activist who passed away in 2006.