User blog comment:Owlfeathers0117/An idea to make surface ships useful again./@comment-24301892-20141217151732/@comment-11135771-20141217153611

What Enterprise said, mostly. There are many smaller ones than 8km though (8km is just the thickness of the rock ceiling); these are more common but less useful, since flying ships won't be able to get through and they only provide a little light. If the idea goes through, I'll create maps of both planets for reference.