My friend and I are looking to start writing our own story, complete with new world and everything that encompasses. I've been looking at designing maps and the world and found this website: http://donjon.bin.sh/ There are lots of useful tools on here, such as the fantasy world generator, found here. When constructed it gives you a good, detailed map, with rivers, cities, castles, forests and mountains: You get a better, closer view on the website. There is also a demographic's calculator. There is plenty more useful tools on here to help with world building.