The quality of ontology alignments is evaluated by comparing to reference alignments and calculating general measures, i.e., precision, recall and F-measure. These measures, however, only provide an overall assessment of the alignments' quality, but do not reveal differences and commonalities between alignments at a finer-grained level such as, e.g., regions or individual mappings. This demands comparative exploration of alignments at different levels of granularity. Furthermore, reference alignments to compare to are often unavailable, which makes such comparative evaluation even more important. To address this issue, we introduce Alignment Cubes which supports efficient interactive visual exploration of multiple alignments at different granularity levels.