Power Cell Final Reward Location?

[Gandrake]

So, I've been able to gather that somewhere on the map, a door opens for getting all the power cells and turning them in, but I don't know where and the information on this game is scattered haphazardly across the internet.

I was hoping the wiki would have the answer, but no such luck. Where are you supposed to go after completing the power cell quest?

[Cacledemon]

I guess there's no reward for YOU in this quest, but for the robot-scientist itself, who can finally meet his friend/or wife? now.