the earliest world i remember was a gigantic city i made with friends, a lot of.. inappropriate stuff i didnt understand
honestly i was so proud of it since it took me so many days to build and thats the beginning of basically the only reason i played minecraft a lot
another thing i remember in the world is making custom recipes for some reason, like 9 item frames with a sign and another item frame, like this
[] = frame
[][][]
[][][] = []
[][][]
deadbush recipe, bedrock recipe, enchanted book recipe, etc.