Ptolemy recognizes that a mapmaker has to make choices, a major one being the subject of the map.

He notes that detailed maps of Europe are difficult to make, because of the many known features and places that need to be legible on a map of reasonable size. As a solution Ptolemy proposes to make single maps of areas where fewer places appear (for some areas of Asia, for example) and make several maps for Europe, where many names appear. Twenty-seven maps are present in most editions of the Geographia, as follows: 1 world map; 10 maps of Europe; 4 of Africa, 12 maps of Asia.