Many people wonder what is actually the best enclosure for a particular species, this got me thinking: What are the best CLOSED enclosures for a species. Just like the thread Best exhibit for this Species, I name a species after which we can discuss which closed enclosure was the best for a particular species. If nothing is posted in this thread for 2 days I will move on to another species. Others may also name species, but do so only a few days after the last post in the thread. I know there are many bad things about these enclosures (they were closed for a reason) but there is still 1 that is the best of all the closed exhibits for this species. Also enclosures that still exist but have been converted to e.g. a different animal species may be mentioned. We will start with the polar bear.