The thesis draws on a range of theoretical and methodological approaches to interrogate some of the ways in which the idea of 'utopia' is relevant to contemporary socio-spatial practices. It does this in two, inter-linked ways. Firstly, the notion of utopia is re-theorised following a re-reading of utopian literature through certain 'non-representational' and post-structural theories (performativity, Actor Network Theory). Secondly, the thesis explores the complex relationship between architecture and utopia. I promote a number of new ways in which studies of architecture and utopia can be related. Crucially, I do this through a 'critical geography' of two ecological buildings: The Hundertwasser-Haus, Vienna, and Nant-y-Cwm Steiner School, West Wales. This meant examining - through mixed, ethnographic methods - the complicated 'performative' meanings that builders and users constructed. This is particularly important because these two examples, and ecological architecture in general, can be associated with various utopian features, but have not yet been explored through a more 'critical' approach. The research drew together these strands to provide a number of often surprising conclusions. The most important was that in addition to (re)presenting visions of comfort, order or political critique, much of the effect and attraction of utopias is that they can in many ways be fundamentally unsettling, discomforting and un-homely. Focusing on three specific themes - difference, the homely and community - the thesis demonstrates this empirically by arguing that utopias are contingent, painful, embodied, anxiety-inducing, momentary, co-relationally produced with non-human actants (including ruination!), and require a tremendous amount of work, whether euphoric experiences of 'escape' or ethical versions of the 'good'. It highlights important ways in which critical geographies of architecture can collect and disperse a variety of emotional, ethical and material concerns (such as utopia or community), and are hence well-suited to the complex demands of contemporary theories and everyday lives.