In Beauval Zoo (France) a few bridges exist over enclosures allow to see some animals from above : Kangaroos, Bush Pigs, Giant Tortoises, Dromedaries, Cheetahs...
They are quite recent, but don't count among the most scenic enclosures (they are rather accessories of other exhibits like the Australian Zone, the Hippo Reserve, the Tropical Dome...), except for the Cheetahs.
There are also bridges that separate 2 different enclosures from each side (Bongos / Bird Amphitheatre, Indian Rhinos / Malayan Tapirs...).