on Mythic Scribes:

Image from The Geography of Transport Systems
Map building is perhaps the basis of fantasy, epic fantasy in particular. JRR Tolkien once wrote, “I wisely started from the map, and made the story fit” (1 2).
George Martin, aside from stealing Tolkien’s RR, also utilized the same process; this is particularly noticeable in how he utilized the Wall as a scale for his maps, and (generally) made travel times fit said scale. In an interview, Martin pointed out how maps are necessary for fantasy, which is a repeat of Tolkien’s argument.
Here are some factors to consider when building a map of your fantasy world.