Was walking around to search the North-East End of the Map just to check my Compass;-)
I found this place. I know it's outside the Official Map, since there is no vegetation at all, but still... Player can see it, and it looks strange.
I uploaded the screenshots of it.
You can see where the water starts, but then it disappears and a huge black hole is in the middle.
I tried to walk in, and there is really wather, I can swim in it, but I can't see, so it looks like you can fly around...