Also, if we get to a point where we can build them from carbon nanotubes, we could make them the size of continents. https://en.wikipedia.org/wiki/McKendree_cy

Also, if we get to a point where we can build them from carbon nanotubes, we could make them the size of continents. https://en.wikipedia.org/wiki/McKendree_cylinder https://en.wikipedia.org/wiki/McKendree_cylinder