During the first third of the twentieth century, Barcelona turned into a metropolis with emerging industry. To confront the growing social problems, Barcelona City Council undertook a renovating educational programme focused on hygienic and natural principles as well as on new active teaching methodologies and progressive education. Thus, a completely parallel network of institutions was created alongside the public schools -- school camps, day trips to the beach, open air schools, etc. -- that aimed at improving the living situation of children, most specifically via the promotion of direct contact with nature. At that time, Barcelona City Council disseminated information widely regarding all these initiatives with the publication, between 1909 and 1933, of around 70 illustrated brochures. The main aim of this article is, using these publications, to present the discourses that were disseminated and built up around the idea of nature and to understand how this relates to the urban environment.