If you mean the stairs NEXT to the Bishop (the spiral ones inside);
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<span class='standouttext'>Spoiler : </span><span class='spoiler'> the prison is holding a Ranaar prisoner, go to the prison (Below temple) and say the bishop allowed you to see the prisoner, to the guard. The Ranaar will tell you where the 'key item' is to unlock the stairs.
If you cannot get into the prison, try retalking to the bishop. </span>
