These great hollow globes of artificial super-metals, and artificial transparent adamant, ranged in size from the earliest and smallest structures, which were no bigger than a very small asteroid, to spheres considerably larger than the Earth. (Olaf Stapledon, STAR MAKER)
A good guide to finding good history. There's a lot of dodgy stuff out there: poorly researched, mainly a thin covering for a warped sense of politics. Take a step back with this article and seek out books that will inform you!