Read this: Here are some cartography tips from the guy who mapped Westeros
Scottish mapmaker Jonathan Roberts grew up playing Dungeons & Dragons in “an ancient farmhouse…so old it is listed in a medieval land inventory.” His interest in role-playing game and the lands around him translated into a skill for fantasy mapmaking, imagining the cartography of fictional lands, samples of which can be found on his website Fantastic Maps. He’s also the designer behind the official Westeros maps for the Games Of Thrones companion atlas The Lands Of Ice And Fire. Wired has an interview with Roberts where he discusses his childhood introduction to fantasy maps, the influence of J.R.R. Tolkein’s Lord Of The Rings maps, and his approach to starting a new fictional landscape. Any cartography nerds out there (and there should be more) will find his creations fascinatingly detailed.