Well, when I found out a class 16 planet, I was very happy.
Still, I have been disapointed that such a planet could not be improved by any means (including the latest terraforming techniques).
Now, this planet is about the third on in my empire as other rather good planets (quality 15 from minor races that I somehow took over) could, them, really be improved. One of them now has 21 tiles to work with...
Why is the wonderful PQ 16 immune to any improvement ?