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It is on the lagoon side of Marvel Superhero Island. And yes, as far as I know, it has been there since the place opened. But I didn't notice it until about a month ago. It is a cool detail that I had not noticed and I figured others hadn't either so I decided to snap a photo today and post it.
I hadn't noticed until just now, but you can actually see a reflection of The Hulk in that photo.