Crumbling floor location

I've just unlocked the desolate dive ability and am trying to find a specific room with a rumbling floor that I encountered near the beginning of the game.

It was a quite large room and I think you initially spoke to someone in there (Cloth maybe). I can't seem to find it though!

Does anyone know where I mean?

I'm trying to avoid finding out locations of too many other spots with breakable floors of possible so don't want to just google them all.