Here is another sign also removed, but only more recently. Once hanging outside of the large wooden gates made out of tree trunks, it alerted guests that an unfriendly Indian attack could occur at any time and the gates may close.
Here is the actual exit from the secret tunnel.
Like any intriguing area for kids, there are other secrets as well. This sign points out one (I guess it is not that secret.) The imagineers definitely knew how to engage not only kids but also adults. How many of us want to explore secret areas? It is the lure of the abandoned building, calling to us to explore and not knowing what one would find.
The most intriguing area for me as a kid and playing on the island was behind this fence. I have always wanted to go back through this gate and look at what was hidden in the trees. Now it is used for storage for Fantasmic.