Thinking that it is possible to do more and better with less, with nothing, n'UNDO becomes a knowledge centre, a think tank, an urban experimentation centre where the materialization of the ideas of no intervention or minimum intervention with a maximum positive impact, are based on the concept of building from subtraction, on the concepts of undoing, not doing and redoing, understood as cleaning, regenerating, recovering and valuing the existing and as a way to improve our cities. These ideas become concrete proposals through a technical office. Proposals that work towards real sustainability: economic, social, cultural and environmental, to improve people's lives. The question is not anymore how we do it?, but what do we have to do? and if it is really necessary.