One thing that I have a really hard time creating is maps.Which is a challenge, because I am having this love affair with sandbox style gaming right now (It's been about a decade, who am I kidding?).
My current (on hiatus) campaign is very heavily map focused. But right now, it's a pretty blank map. Some randomly generated geography and little else. The setup is that the world is very new and the PCs are there to explore and tame it.
Since this is a D&D game, there are dungeons, so on top of that blank, still to be explored overland map, there are smaller dungeon maps.
The downside of this is that the stretch of campaign that I have run so far has been on Roll20 (because pandemic), and it has not been easy importing all of those maps. It actually got sufficiently annoying that I stopped trying to simply import them and took to reconstructing them using Roll20's own map tools. That's one of the reasons the campaign is currently on hiatus.
I'm looking forward to getting to the point where the players have explored and made their own mark on the map. But that is in the future.