@Cinera @ShishioIsBack @Sentinel those chapters all prove to me though that Onigashima isn't really big. There are a lot of direct perspectives that illustrate it. For example this:
Zoro is seen among these "mountains". King all the more. Even the building in the background, which has 2 floors and sits among those mountains, is like 1/5 of these mountains. We also saw ships being pretty big when right next to these boulders:
Those boulders are certainly a couple of 100 meters big, but certainly now in the Kilometers range, like 5km. All these "calcs" are inaccurate since they do not consider perspective. But here we have a 2 floo building that sits right within the boulders. Plus the stairs leading into Onigashima, which have the width of 1-2 humans and are leading right into Onigashima.