I remembered seeing similar Stolpersteine in Nuremberg, so I googled and found the official German website of the project. According to this, there are Stolpersteine in more than 500 cities/towns/villages in Germany, as well as in several other European Countries.

The project wants to keep the memory of all the victims of Nazi deportation and murder alive, Jews, gypsies, homosexuals, those persecuted because of their political positions, Jehovah's Witnesses and others persecuted for their religion, and the victims of euthanasia.