User blog comment:Ramallah/Mass Effect 3 details revealed/@comment-3535404-20110421100634/@comment-3546856-20110421104647

A blue sky isn't an earth exclusive. Other planets can have blue skies. You just need a planet with transparent gases that have molecules that are smaller than light waves. And the architecture itself could be anything. I see similarities to the Citadel and many other buildings in previous Mass Effect titles.