The Stolpersteine (literally "stumbling stones") are World War II memorials placed into the sidewalk in places where Jews and other victims lived until they were deported and killed by the Nazis.
Each stone represents a single person, and includes a brass plate engraved with their name, birth year, deportation year, and date and place of death. In Oslo there are 236 such stones as of November 2017.
At snublestein.no (in Norwegian) you can see where the stones in Oslo are located and find information about each of the commemorated individuals.
About the Stolpestein project
The project was started by German artist Gunter Demnig in 1994, when he placed the first stone on the sidewalk in Cologne. Since then more than 60,000 stones have been placed in 22 European countries.
In 2010 the Oslo Jewish Museum brought the project to Norway and placed the first stones at Calmeyers gate 15, where the museum is located in a former synagogue. The house in front of the synagogue was home to 28 Jews in 1942, and 19 of them, several of them children, were deported and killed in Auschwitz. Each of these 19 victims are remembered with a stone outside the museum.
The other 217 stones in Oslo are spread across large parts of the city, including Frogner, Vika, St. Hanshaugen, Grünerløkka, Tøyen and Grønland. The stones on the photo above are located in Uelands gate 14 near Alexander Kiellands plass.