I find this very fascinating. Is there a site that discuss the kind of materials (never mind if they're non-existent, as long as they're plausible, i.e. within the realms of known physics) and technology needed to construct such massive vessels that wouldn't collapse under its own...ok not weight, since they float in space, but I imagine the moment thrusters are fired the internal structures would be pushed and pulled in different ways (the stresses on the system, and how the internal subsystems adapt mechanically may create a myriad of interesting noises/visuals perceptible to the inhabitants within)