Above is a rough idea of the tower, looking top down, and the spiral catwalk rising up from the middle (best I could do, really ... perspective has never been my forte). The lines to the bottom are there just for effect. At the top, you can see the hole in the ceiling; the black object in front of the hole is part of the steep ladder that extends up into the hole, enabling access.
The party reaches the point where they are now when it becomes evident that the 'flickering' I mentioned before is the shadows of people moving in front of a light source. As far as you know, said people do not know anything about your existence; they are calling orders to each other.
One is shouting over and over, "HAUL! HAUL!" and each shout is followed by the sound of loud grunts. There's also something squeaking incessantly, and the sound of something heavy and soft landing.
The battle sounds underlying it all are louder, too.