The Erased Foundation Spiral Markings are a series of heavily weathered carvings discovered beneath accumulated rust mineral deposits and maintenance residue within Furnace Hall C. Only fragmented sections remain visible due to age erosion and repeated surface treatments conducted across multiple restoration periods. Surviving portions reveal spiral forms consistent with recurring motifs documented elsewhere throughout the Archive including maritime records foundation structures and recovered cartographic markings. The carvings appear significantly older than surrounding maintenance systems suggesting they predate later modifications to the western halls. No complete inscription survives and any associated text has been lost through wear or deliberate removal. The markings were uncovered during routine furnace maintenance and subsequently removed from the exposed surface during cleaning operations. Documentation survives through sketches photographs and maintenance notes recorded at the time of discovery.