In the last few centuries, a metallurgical industry based on forges driven by water wheels developed in many European valleys. One such area is the Old-Polish Industrial District (OPID) in Central Poland, which is one of the largest of this type of industrial center. Metallurgical activity developed here from the Prehistoric to modern times. The transformation of metallurgical technology led to the collapse of production, and the ongoing renaturation obliterated most of the traces of former industrial activity. The Magnetic Spherule Separation method used so far in Western Europe, and recently in Poland, has been able to detect traces of former metallurgical activity preserved in alluvium. Fluvial deposits contain microscopic, perfectly spherical iron hammerscales formed during metallurgical production. The results of the study of the alluvium of selected rivers in the OPID indicate the presence of iron spherules of various origin and facies in the sediments of the floodplain, which accumulated during the period of metallurgical activity and were redeposited in modern times. This allows us to estimate, among other things, the age, rate of accumulation and impact of anthropopressure on sedimentation conditions.