the monument that was allowed to decay

The weirdest part of Ilha is the monument opposite Fortim de São Lorenço that was left to erode and decay. I’m not sure if it was once part of the fort or something bigger but got destroyed by a cyclone or something but I find it weird that, in an island where many historical buildings are still intact, this particular one would be left to decay. My guide didn’t know what it was, I found no information on any brochure or the internet. I’m still wondering what the story behind it is.