Carvajal House is the crystallisation of a deep reflection on the role of courtyards in Modern Architecture. Modern architects had initially dismissed the use of courtyards on their designs, because they used to associate them to the traditional spatial conception, characterised by introversion and a clear conceptual distinction between inside and outside. After this initial rejection, the courtyard was gradually reintroduced, and paradoxically, we will show how it was in fact an element that led to the evolution and development of modern spatial concepts, such as openness, phenomenological transparency and phenomenisation of space, because it constituted a way to integrate concavity again. The aim of this paper is showing how these modern concepts appear clearly in the interiorised courtyards of the Carvajal House, revealing the decisive role that they had in the evolution of modernity. We analysed the formal order and the perceptions that a person can experiment throughout the spatial sequence, from the access to the surroundings of the courtyards. This makes clear how the courtyards are fundamental elements in the design strategy, both at a morpho-syntax level (as the seed of the formal logic) and at a perceptual-emotional level (qualifying space as the stage for life).