Plot option: Adventurers infiltrate under the guise of prisoners to complete a mission. For example, free a prisoner and escape with him or find out the terrible secrets of this place. Also, adventurers can force their way outside. Perhaps they will first send out reconnaissance under the guise of an inspector or a guest.
In the meantime, you yourself have to answer the questions:
Is this an official prison or is it owned by a cultist cell?
What’s above the stairs? The lord’s castle? Forest Glade? City center?