Like @snowleopard I am interest in your response @twilighter.
I quite like Planckendael outdoor one which is, in my opinion, a good mix between nature/enrichment/elephant behaviours. Of course, Cologne indoor is a higher level but a little bit too concreted.
This is difficult question, since the both facilities are terrific. I would say Planckendael is better for the animals, while Cologne is better for the visitors
