We talking just map design? Probably 3/4 of Alola, which is more than I can say for something like Sinnoh and arguably Kalos. To be fair after Alola you had the exceptionally bad Galar and the subpar open world design of Paldea, so it's not really that great of an accomplishment. If we're talking last great map design instead of just good, probably Hoenn or Unova if you're being exceedingly generous (I'm not, it's just good). On the more thematic side, that's also a good question and it also probably goes to Alola because they've been skimping on a lot of that stuff in Galar and Paldea, and Kalos was mediocre and Unova was okay at best.
>>56071883Nah, Sinnoh does have memorable areas, but they're usually themed a little differently than maps from previous games. Sunnyshore, Snowpoint, and Hearthome immediately come to mind as towns. Unfortunately they were still re-using assets a little too much during that phase, which is somewhat understandable given they had to hire more 3D people during BW's development, and even Platinum didn't improve on it much.