"Originally we had citizens up on the street level shooting RPGs at the Citadel, and we were planning to have an all-out assault on the Citadel underway. But at a certain point it felt better to have the player all alone entering the Citadel, with only sound being eerie creaks and groans of the Citadel itself. It was more in keeping with the classic quest theme of a lone knight entering the fortress of the enemy, which was the feeling we were trying to evoke."
CW3D took a note on an icon of the game's 12th chapter - "Our Benefactors". On it one can clearly see explosions on the Citadel's hull and trails of RPG rockets. More than that some details on the maps are missing, such as sewer pipes and buildings, which it seems were added later, as well as the fog. You can compare both, chapter's icon and in-game screenshot made at the same place on the next images: