That was a crater at the bottom? I'm not sure I ever saw one (except Ngorongo Crater) in all the games I played...
Hehe, yes, indeed.
A giant map only spawns several of this feature, quite rare.
Edit: I was playing the game and drinking my homemade wine when I suddenly stopped playing, just staring, at the atrocity I'd seen a thousand times before. before I knew it I had quit the game and was constructing a new model in blender. 20 minutes later the model and texture was finished and I thought, what the hell happened and uploaded it here.