The Getty Thesaurus of Geographic Names is an interesting resource: it catalogues more than a million place names and their relationships (such as equivalence, or different names for the same place, including which is preferred; and hierarchy, such as the county to a town, or a province to a county). There are no maps, and the geographic coordinates are there largely for reference purposes, but useful, I think, for anyone with an interest in place names. Via MapHist.