A stolperstein (] from German, literally "stumbling stone", metaphorically a "stumbling block" or a stone to "stumble upon", plural stolpersteine) is a cobblestone-size (10x10 cm ) concrete cube bearing a brass plate inscribed with the name and life dates of victims of Nazi extermination or persecution. The "stolperstein" art project was initiated by the German artist Gunter Demnig in 1992, and is still ongoing