In a unique architectural style of the twentieth century, Ludwig Mies van der Rohe (1886–1969) realised a new type of modern space defined by an unobstructed clear volume enclosed by framed glass skin. This is generally referred to as Mies's universal space and this paper will attempt to interpret Miesian universal space in terms of the idea of tectonically defining space. Mies referred to the term ‘tectonic’, or ‘architectonic’, as constructive appearance exposing the skeleton structure. For Mies, the concept of tectonic was connected to a glassy materiality that permitted the unambiguously constructed appearance of a skeletal structure. He regarded the glass skin as a ‘tectonic means’ and the instrument of a new art of building.