Do you believe that the earth we live in is hollow? and that there is another advanced civilization there?
Why don't you go and ask flat earthers is earth hollow? I am sure they will find some pictures and videos on youtube
If the earth is hollow we'll all be crushed flat by gravity and we would not be existing and I would not be able to answer this forum. However, I believe that thwre is no other life forms and that we are inherently all alone in the grand scheme of the universe. An insignificant speck of life in an otherwise all consuming universe