Visualizing the events described in a text is crucial for constructing a rich and coherent visuospatial mental representation (i.e., situation model) of the text. According to current reading comprehension theories, the construction of such a situation model likely involves all sensory modalities. However, at present these insights are hardly used to inform reading comprehension strategies for improving the understanding of text. To provide more insight into the different ways visualization can be used to encourage readers to build non-linguistic representations of text, this paper classifies the visualization strategies that have been studied and discussed in the literature along internal-external and unimodal-multimodal dimensions. Thereby, educators and other readers are presented with a contemporary collection of visualization strategies to improve reading comprehension that could inform practice and provide a basis for further research.