In 1972 at Berlin-Lübars a prehistoric site of iron-melting was excavated. With the aim to describe the technique of iron-melting, slags were analyzed chemically, microscopically, and physically. It was found that it was a melting place and not a forge. Sedimentary iron ores were transformed to bloomery iron with an output of 30-45% iron. The shape of the slags indicated that wind was used for blasting. By comparison with similar constructions and by the age of the pottery found, the melting-place was used in the 3rd century A.D.