The Clore Rainforest Lookout at London Zoo comes to mind.
Constructed in the sixties as the Charles Clore Pavilion, it was the zoo's take on a small mammal house, housing, for quite some time, more mammal species than any other UK zoo housed in its entire grounds. However, despite being two levels, the exhibit standards aged the worse in the zoo, and as part of its 21st Century recovery from the near death experience of the nineties, massive renovations had to take place. The upper level was converted to 'Rainforest Life,' the rainforest house from which the building derives its current name, and the lower level to 'Night Life,' a nocturnal house.
Both of these used to be far better. Rainforest Life used to feel extremely lively, full of free-flying birds, while armadillos scurry across the undergrowth bringing life to the forest floor. Currently, the whole exhibit feels incredibly barren. However, all the birds have either moved to the Blackburn Pavilion bird house or departed the collection, and the armadillos have passed away. Currently, only the Rodríguez Flying Foxes, who spend most of the day asleep, bring aerial life to the enclosure, while only wild mice and rats who snuck in bring life to the forest floor. The only real highlight are the Southern Tamanduas, a breeding pair and their offspring, who are regularly active and most likely the last remaining individuals of the nominate subspecies in Europe.
Even when the birds and armadillos were present, it was still an extremely weak rainforest house. The glass roof of the main mixed species exhibit is several metres above the dark, concrete roof of the visitors walkway, which means even though it is completely barrierless, nothing but the occasional callitrichid leaping along the walkway reminds you that you are actually sharing space with the animals. Raise the roof of the walkway, bring back some free- flying birds, and bring something lively to the forest floor (the zoo actually houses a pair of armadillo in the off-show Casson Terraces, the indoors for the Babirusa, that are only visible during displays), and you have one of the best small rainforest houses in the country. But as it stands, you have a mediocre and uninspiring house; not bad, but easily improved.
As for Night Life, it just feels so empty. Several species have three or four enclosures where just two would easily do the trick. Of course, the animals aren't complaining about more space, but it doesn't take a genius to realise that there used to be far more species present. Some enclosures are unapologetically empty, and there are entire walls where no enclosures are present, but such a thing could easily be added. Its agonising. That said, with Potto, Grey Slender Loris, and Moholi Galago, as well as Aye-Aye in a separate nocturnal habitat upstairs, I really shouldn't be complaining. And, of course, the good thing about having less species, is that most enclosures are far more spacious than what can be found at other nocturnal houses.
The Clore is not a bad exhibit, but compared to its past self and compared to what it could become with slight changes, it is massively underwhelming, hence my including it in this thread.
