According to the plan this roofing shaft appears to connect to chamber I on 12 with K beyond it which is the extent of the mine on this level to the east. To the west is chamber H, then a short level connects to the whole of the flooded eastern section - A real "lost world"
But given some inaccuracies between the plan and what has actually been found in the eastern section above floor 9, eg the discovery of inclines and winders not shown on the plan etc - who knows what's really down there.
I wonder if there are lots of artifacts below the water: - stairways, complete Jwmpers (very rare), more evidence of the interesting mechanisms they used on the inclines for example?
Has there ever been any plans to dive here?
'I wonder how many breakfasts, and other meals we have missed inside that nasty clockless, timeless hole?'
'The Hobbit'
J R R Tolkien.