Where are the fortress rotation controls?

Hint 1 of 7:

The controls in one of the brother's rooms are *not* the real thing.

Hint 2 of 7:

But they are a good simulation -- first learn how they work here.

Hint 3 of 7:

You can't get to the real controls until you've first managed to get the
elevator working.  See the previous question for more help there.