I made a big map for my D&D game and turned it into a poster for use during the game. It’s easily the most detailed thing I’ve ever drawn; it took me about a year working on and off on it in my spare time, mostly as a break from my dissertation or as a way to wind down in the evening. It’s entirely hand-drawn except for the lettering; I scanned a lot of 8-1/2″x11″ pages together, then edited them.
Here it is:
As you can see, it’s pretty detailed: