The paper draws upon a pedagogical project that addressed the design of spaces for cohabitation, of new alliances between buildings and the natural environment, in the context of the contemporary city. First, it explores how the fantasy of the large-span, glazed, vegetated environment has shaped visionary projects, marking a shift of attention from the physical to the physiological and from the tangible to the intangible qualities of space which resonates with contemporary concerns on design for sustainability. Following the evolution of the glass house from a place of nature preservation to a vehicle of experimentation into new ways of inhabiting the city, it then examines the contemporary relevance of such a building type and how it has fostered new architectural narratives on the co-existence of people, buildings and plants. Second, the paper presents the methodology practiced in a postgraduate design studio at the AUIC School/Politecnico di Milano which aimed to raise awareness among students about the relational dimension of architecture and the reciprocal exchange between design and research. It discusses how, by revisiting the glass house figure, the studio output set out to generate new conceptual, aesthetic and design definitions of the architecture of the in-between, of spaces of transition between the natural and the manmade, inside and outside.