It opened in 1974 and was actually the world's first domed rainforest exhibit. I'm sure that the Topeka Zoo was massively popular during the 1970's with this building.
See, I'd heard itwas the first but I've also heard it wasn't. I guess the answer is, it was the first domed rainforest building as opposed to the first rainforest building? I could definitely see it being a wonder for it's time. It's got some beautiful, lush growth in it.