Instead of falling for the ever so provocative ranking of the "best" (a rather dubious undertaking with Omaha's zoo involved

)-why not make a list of all nocturnal houses/exhibits worldwide in zoos instead?
Off the top of my head, I would mention:
-Grzimek House, Frankfurt
-Nocturnal exhibits, Berlin Zoo
-New Zoo, Poznan
-Papiliorama-Nocturama, Kerzers (CH)
-Indonesian Nocturnal Corridor, Prague
-Nocturnal/Small Mammals House, Plsen
-Some exhibits in the Reptillium, Landau
-Small, but kinda 'cool': African Nocturnal Hut, Jihlava
-Nocturama, Antwerp
-Glossophaga bats in the rainforest house, Krefeld
-Fruit Bat Cave in the Villa Dracula, Munich
-Bat Cave in the Borneo House, Vienna
-Bat Caves in the Biodome, Montreal
-"Underground Zoo", Dresden and soon the new "Underground" zoo in Osnabrueck
-World of Darkness, Bronx Zoo
-Zoo Saarbruecken and Erfurt Zoo
-Cincinnati, Cleveland, Columbus
-The kiwi house at Wilhelma, Stuttgart, was quite interesting, but does no longer exist; the still existing nocturnal exhibits are, similiar to several others mentioned here, upgradable..
-Twilight Cave, West Midland Safari Park-never been there, so ?
-Night Safari, Singapore
Not to mention zoos like Salzburg, Dvur Kralove etc. offering zoo nights a few times a year...