The Centripetal and Centrifugal Citadel from Mass Effect

S1, E4: Kyle Hill and AI have made it to The Milky Wa---wait a second! Not yet. The two have to wait a bit longer and take a stop at The Citadel from Mass Effect. Twice as large as the Hadron Collider and home to 13.2 million organisms, it's kind of a big deal.