This wide spacious cylindrical chamber seems to be a sort of three dimensional crossroads for the Old Mine. Over a hundred feet in diameter and at least as tall, it’s dominated by two large vertical shafts, one that vanishes upward, entering from the roof and another fifty feet away that vanishes into its floor.
The upper shaft looks familiar, likely the Old Main Shaft you encountered in the upper level. That shaft ends at this chamber. Much of the chamber's space is given over to a set of cranes, pulleys and landings that were evidentially used to transfer the large round shaft platform from the top mechanisms that raised it to the upper chambers to a similar set of mechanism that lowered it further into the mine.
You suspect the miners had evidentially dug so deeply that a single set of pulleys and ropes were no longer strong enough to carry a platform all the way from the top of the shaft to the bottom.
The mechanisms were obviously originally powered by a large horsemill located near the center of the cylindrical chamber, where a team of horses walked endlessly in a circle to turn the central axel and impart power to the lift.
The team of horses are still there, turning the lift. Still there after a fashion, though they have changed into something monstrous.
Cloaked in clouds of roiling smoke, their manes, tail, and hooves wreathed in flame, their eyes glowing red, the horse shaped creatures are still harnessed to the wheel, turning it with great speed.
The lift to the lower levels has been unmounted from its moorings and lies discarded to the side, instead of ropes and pulleys the massive engine only dredges a visible plume of darkness from the depths of the shaft. A cloud of inky black rises from below creeping across the roof of the chamber and vanishing up into the shaft toward the upper levels of the mine. Inside the rolling cloud of darkness you can make out movement, the occasional glimpse of motion, though you cannot make out any detail.
Off to the side, a gaunt, ashen fiend with leathery wings supervises the machine. It carries a long bullwhip in one hand, which it uses to direct and drive to greater efforts, the tip of the whip cracking out occasionally to lash the monstrous demonic horses, it’s sting forcing them to greater exertion. The other hand grasps a shepherd's crock.
The wind from the chamber blows strongly out the tunnel entrance, surprisingly cold, almost artic. The wind carries the faint scent of dried blood and old rot.
There are four exits from the room, not counting the tunnel you came in by.
The Old Main Shaft enters the top of the central chamber and exits the floor
The entrance from the Old Baracz Chamber enters about midway up the cylinder directly across the Main Shaft from the horse mill. This tunnel continues out the opposite side behind the horse mill
At the very bottom of chamber you can barely make out a low tunnel off the side, leading downward and away from the main shaft.