Isn't Citadel a name from Mass Effect? ![Tongue :P](http://universesandbox.com/forum/Smileys/default/tongue.gif)
No, it's from Half-Life 2.
Both actually, but since I love Mass Effect it came from Mass Effect
![Wink ;)](http://universesandbox.com/forum/Smileys/default/wink.gif)
The definition is "A citadel is a fortress for protecting a town, sometimes incorporating a castle.
The term derives from the same Latin root as the word "city", civis, meaning citizen."