Hi,
I know of no elephant exhibit in Europe which has naturalistic both inside and outside yard.
Indoor houses I know of:
Dresden has nice tropical hall (see Zoolex website).
Rotterdam has attractive fake trees.
Dvur Kralove, judging from photos, has interesting building for it's African elephants with fake baobab tree. Warsaw also has such tree.
Leipzig seems interesting from photos.
Outside enclosures? I guess some safari park with huge grassy area.
Berlin zoo has several old oaks protected by wooden tubes, as well as a patch of trees protected by a wire. Overall, very pleasant. This zoo is generally marvel of design.
Heidelberg has carefuly designed protected vegetation, mixed exhibit with deer and nice pool.
Basel African yard stricken me as interesting, although barren. Has well designed rocks and tree trunks recalling dry season in Namibia (theme of this part of the zoo). And occupied stork nest on top of the tree trunk in the middle of the yard!
Overall, I agree that good elephant enclosures are still a future. BTW: did you see that?
http://www.leszoosdanslemonde.com/html/etudes_zoologiques/elephants_dyczkowski_11_2006.pdf
For snowleopard:
In Europe at least 20 zoos stopped keeping elephants. About 20 zoos have space and buildings and breeding herds. Several zoos have non-breeding herds of aging females and juvenile bulls. I guess in the next 10 years there might be 40 zoos which stopped keeping elephants and 30-40 zoos with breeding herds.
You can see nicely dynamics of asian elephants in Europe on
Zoo Elephant - Asian Elephants at the Zoological Gardens of the World I wonder if any enthusiast wants to make the same website for African elephants?