In the era of sustainability, improving the general public's understanding of such issues is critical. Geovisualization, which converts complex geospatial data into a visual format, is one method to promote comprehension. Specifically, recent studies have started to investigate methods to engage learner themselves to explore geovisualizations in informal environments. The procedure of data exploration is to make observations, develop questions, and generate hypotheses. To deepen such process, Ma et al. (2012) designed a museum exhibit to afford the learner to link to another data in solving questions of one data. However, including further attempts to improve the system (Ma et al., 2015; Hseuh et al., 2016), most learners were limited to making simple observations in a particular data. Therefore, this research will look into staff facilitation as an alternative approach to support cross-data exploration. A design-based research will be conducted to iteratively refine a model of facilitation. Data collection is planned to be done by video and qualitatively analyzed based on constructivist grounded theory. The study hypothesizes that the design principle is to utilize data-connection not only for answering questions to the previous data but also to trigger another cycle of inquiry to the next data. Further design strategies to implement such principle is to "prompt questions that require data linkage", "allow the learning goal to change after data linkage", and"suggest data that possess a similar structure of relation".