The people of Val di Susa (Italy) blocked the construction of the new high-speed railway line that should connect Turin with Lyons (France). This project is regarded as a strategic achievement for the economic development of the European Union, but local communities have a different concept of development and are asserting their rights through ad hoc experts’ reports and the production “from the bottom” of new specialised knowledge. We shall describe these events as a case study to put ecological democracy to the test of facts, also through a comparison with the experimental actions taken in some Southern countries of the world. From Europe to Brazil, the debate on health and environmental risks resulting from modernisation is upsetting democratic societies and urging new forms of participation in the decision-making process. There is a clash between different “concepts of the world”, in which communication strategies play a crucial role and from whose outcome the society in which we wish to live in will emerge.