I still think the central core is too big to be just a lift shaft (perhaps it's just a dodgy matte).

If you look at the set the the lift sits in the middle of a circular column just a bit bigger than the lift itself.

If you look at the matte the column on the left is much too big to be the same structure (look at the doorway leading out from the walkway, it's about the size the opening of the lift but the circumference of the column is many times larger).

I think the lift shaft runs inside the column in the matte (if we are to take it literally) but there's much more to it, enough for many lift shafts of the same size which is why I suggested that the pit is just another chasm but one running down the centre of the tower.

If the matte was changed most of these problems would disappear.

It's not a good matte anyway, some of the walkways go to nowhere.