The elevator is really just a cage in the floor, right? Outside the hall, i the courtyard, there is a small elevated platform with a symbol in the middle.Stepping on the symbol will raise/lower (depending on the current state) the cage/elevator. I think there is a key inside it ... the portcullis key?
Now here is a challenge for you .... get your party inside the elevator, in its lowered state. It can be done ... I did it once (and was sorry
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Tools for Wizardry(r) 7