Despite their recent development (see Chap. 6), geo-ontologies still represent a complicated conundrum for most experts involved in their design. IT/computer scientists use ontologies for describing the meaning of data and their semantics to make information resources built for humans also understandable for artificial agents (see Chap. 2). Geographers pursue conceptualizations that describe the (geographical) domain of interest in a way that should be accessible, informative, and exhaustive for their final recipients (see Chaps. 2 and 6). In this context, philosophers/ontologists should offer conceptual solutions for carving nature at the joints and choosing how to categorize all the entities belonging to the geographical domain. This chapter aims to combine assumptions and requirements coming from these different areas of research, in order to show what categories might complete the current domain of geo-ontologies. The issue is approached by thinking of such a domain as a whole, composed of two different levels of categorization. The first level concerns the IT components shared among different ontologies. The second level deals with contents, for which (philosophical and) geographical analysis can include categories that do not appear at the first level.