First detailed mineralogical investigation of early medieval slags indicated that in the second half of 12th century, large metallurgical complex, where silver production based on cupellation process, has been active. Our Pb isotope analyses of smelting remains suggest that Pb needed for the cupellation originated probably from mines in Poland. Ettler V., Johan Z., Zavřel J., Walisová M.S., Mihaljevic M., Šebek O. (2015): Slag remains from the Na Slupi site (Prague, Czech Republic): evidence for early medieval non-ferrous metal smelting. Journal of Archeological Science 53, 72-83. (DOI)