Mothership's role in Story

i think that the mothership is a city, but because it has leaders of the conclave piloting it, it focuses their power as well as that of the protoss living on it to cast very powerful spells.

 

i think it is the uber unit that they use in case of emergency lol. and i also think it's a small city. anyone else think the thing inside the mothership's dome looked like a city? of course that may just be the quality of the video.