Christopher Tolkien drew the maps for The Silmarillion and Lord of the Rings. I first learned to draw maps for my D&D games by copying the way he drew the different features. Here's how to draw a fantasy map in that style.
https://www.youtube.com/watch?v=yBrnfSWVyD8
Here's another video on the subject:
See if you can spot the inaccuracies in the lore on the second video. But you gotta love that intro!
One more video, this one a time-lapse drawing Mordor.
https://www.youtube.com/watch?v=CWcW_JiLTOk