Mies van der Rohe, together with Lilly Reich, had a long period of collaborations in exhibition proposals, among which those carried out at the 1929 Barcelona International Exposition stand out. The exhibition performances in Germany have had a recent echo in publications and studies, while those in Barcelona remained shadowed, perhaps due to the dazzling focus that international criticism had placed, at all times, on the German Pavilion in Barcelona. Those shades of Barcelona also affect what was published about the 1929 Pavilion and even its reconstructed version from 1986. The revisit now allows us to reflect on the representation and memory of that performance of Germany in Spain in the twenties, on the doorstep of the darkest period in the modern history of Europe and Spain. The methodology followed in the research has been based on looking at the margins. After analyzing what was published about Mies's exhibition career and in particular about his performance in Barcelona, we opted to change the lens and lens of our cameras. Filter the luminosity that radiated the figure of Mies and his Pavilion, and thus be able to surround them to reveal the hidden. To the complexity of the organization of an international exhibition are added the relations and agreements between the intervening countries, a kind of political "dust free" that is never defined and that intermingles with the constructive dimensions of the event. The figures, recognized by all, from Mies van der Rohe and Lilly Reich have been joined by other characters such as Georg von Schnitzler, Enrique Domínguez Rodiño, Karl Strauss, all of them essential for the inauguration of the German Pavilion, its exhibition facilities and for the celebration of the German Week in Barcelona, possibly the most important diplomatic events of the 20th century in the relationship of both countries.