A preserved structural access route located beneath the western furnace halls. The stairwell predates most documented archive construction and displays architectural features inconsistent with surrounding preservation corridors. Stonework throughout the descent contains heavily worn spiral markings and evidence of repeated maintenance spanning multiple historical periods. Recent observations recorded condensation formation bell-responsive vibration activity and low-frequency mechanical resonance originating from levels below the documented archive floorplan. During a recorded bell event the stairwell transmitted rhythmic vibrations consistent with rotational or alignment-based systems operating beneath the foundations. Historical maintenance marks and replacement fixtures suggest the structure has remained in continuous use for an extended period despite limited surviving records. A soot-covered inscription discovered on the handrail may indicate a connection to bell-cycle protocols and restricted descent procedures. Investigation remains ongoing. Preservation priority remains active documentation of the location and associated phenomena.