It's actually hard for me to comment objectively on this because I'm biased.
I have a short-list of favorite locations for the VMS "map" (after looking at hundreds of towns near water and trying to match them up with the "map" topology) and Naples is one of my top picks.
I've tried to stay open-minded about that "triangular" thingie, maybe volcano, maybe springs coming out of a mountain, maybe geysers or steam vents, but I think volcano is certainly one of the possibilities and I think it MIGHT be possible to track it down to a specific feature if the objects around it fit well enough.