This article describes the UCR Spatio-temporal Active Repository (UCR-STAR). UCR-STAR is a visual catalog for big spatial datasets. Rather than a boring tabular listing of datasets, it provides an interactive map interface that allows users to explore these datasets to assess their coverage, quality, and distribution. This article describes both the functionality of UCR-STAR as well as the underlying system architecture. We believe that this article can help the research community by explaining how to realize research ideas into a workable product.