44. The Citadel
First Appeared: Mass Effect (2007)
Founding Father: Casey Hudson and Preston Watamaniuk
Notable Residents: Commander Shepard, Joker, Liara, Kiadan, Archangel
Though most non-gamers know Mass Effect for its heavily publicized but hella anti-climactic sex scene (alien sideboob, anyone?), everyone that stepped into the immersive world of this sci-fi RPG remembers the Citadel, the massive space station shaped something like a pentagram. Its population comes in at a whopping 13.2 million. We'd certainly like to dirty it up with some properly hardcore extraterrestrial sex (yes Katy Perry).