This paper tests the dictum that 3D isovists are easy to generate but hard to represent. In the first section of the paper, we review eleven past attempts to represent 3D isovists, ranging from 1996 to 2014. We attempted to select the widest range in terms of approach, novelty and significance to the field of spatial analysis. In the next section of the paper we introduce three new 3D isovist representations, termed the ‘Contour Isovist’, the ‘Tri-planar Isovist’ and the ‘Circumvoluted Isovist’. In the final section we evaluate these new 3D isovist representations using an online questionnaire, aiming to compare the representations and to determine their clarity, information-content and simplicity. We invited an expert set of participants (resultant n=20), all of whom were familiar with the use of 2D isovists for research purposes, to take part in the questionnaire. The result of the evaluation was that two of the isovists, the ‘Contour Isovist’, the ‘Tri-planar Isovist’, we deemed to be relatively successful and hence have potential for future development. The contribution to this paper is twofold. First, the two successful 3D isovist representations are a contribution to the field and, second, the method of evaluation. We conclude that insufficient research has been conducted into the efficacy of space syntax representations.