Wonderful stuff! I can also see having a mysterious culture known only from a few sealed dome cities that are uninhabited but almost impossible to gain access too. Also, does earth have a beanstalk or a series of beanstalks joined by an orbital ring? If so (and at least one beanstalk would be exceptionally cool) then it should likely be either by the Builders or (more interestingly) the Lifemakers - for niftiness about living beanstalks, take a look at Larry Niven's Rainbow Mars (which is surprisingly good & fun, and could also have some useful inspirations)