We know from the game that Hugo's cure is nowhere to be found on the island (at least not in the adventure as it unfolds). But Hugo's dream in the first chapter, where he dreams of this island, you can see La Cuna's "Las Madres" to the right of the crack that Hugo goes through.
The building Hugo sees once he crawls through the crack in the mountain, looks very similar to the buildings where the ceremony takes place, and the general position of the mountains look very similar in angle to where the Fort is.
Also, where the children and Sofia emerges from the sewers after the ritual, it is also in that general direction, tying the style of buildings with the building in Hugo's dream.
Of course, it can't be affected in the game, but has anybody any idea of where this mysterious water source that the kids could not find to cure Hugo could be? I would like to explore the island map a bit more to see if I can find the location of Hugo's dream on the island.
