The architectural theorist and practitioner Bernard Tschumi asserts that enquiring and working at the limits of a discipline expands our knowledge and experience. Within this thesis I examine the limits of architecture as they relate to the non-material and the nonvisible elements of space. As Mark Wigley observes in his essay on atmosphere, architects, at different times, have sought to understand, capture and control the otherwise ungraspable aspects of space. The elusive nature of such ephemeral architectural aspects and elements makes them hard to manage and map. Their examination provides a challenging exercise within architectural research. Atmosphere is such an elusive element; as Zizek would call it, it is that which remains always as a backdrop to daily life. It seems to vanish when subjected to conscious scrutiny. Non-visual sensations such as sounds, smell, textures, temperature, clearly constitute invisible elements that are notoriously difficult to represent. As a further example, event, the way in which a space is or could be deployed or inhabited over time, provides another unpredictable and ambiguous design consideration. Spaces relate to performance. The performance of a place constitutes its nature, character, function and meaning. However, the complexity, changeability, and potentiality of spatial performance render it as something abstract and non-representable. As Steven Connor, and Jonathan Hill, amongst other theorists, observe, new media, electromagnetic fields, and digital gadgets, also constitute invisible elements of space. They create invisible fields, territories, links and boundaries, affecting everyday spaces and relationships. So a typology of the elusive and ephemeral characteristics of space would include: non-conventional materials, elements changing over time, electromagnetic fields, electronic equipment, nonvisually representable sensations, situations, processes and events. Attending closely to these themes reveals some key questions. Why do these themes appear (or re-appear) now, at this particular moment in history? How are they related to contemporary thought, practice, and to current shifts in society, culture and technological development? New technology, new means of representation, and emerging design media change both the way in which we inhabit space, and also the way in which we understand and represent it. Digital media allow us to record and represent time and duration. Hence, events and situations occurring over time can be documented and studied. Subsequently, new media can also function as a new tool to think about space, and for designing accordingly. As Marshall McLuhan claimed in the 1960s, the emergence of new digital media has caused a ‘shift in the sensorium’ and has readdressed the significance and role of experiencing and sensing other than through the visual sense. In this thesis I discuss in turn a series of limits and the qualities of the spaces that they reveal. Each chapter title is based on a binary and a theme that indicates its transgression: (a) the visual versus the non-visible – the sensuous (chapter 2), (b) the discourse about the formal versus the material – the performative (chapter 3), (c) the physical versus the digital – the hybrid (chapter 4). In order to examine these themes and explore the design potential they entail, I review relevant literature in parallel with the conduct of a series of design experiments. The experimental processes deployed are of three kinds: (1) mapping and documentation of sensory situations, (2) design experiments that challenge the issues discussed and (3) real-scale interventions that test some of the design ideas at a 1:1 scale and in an actual place. The latter includes a major installation at the 2009 Venice Biennale on the theme of Athens by Sound initiated and designed by a team involving the author.