The First International Workers' Olympiad was held in 1925. The winter games were hosted in Schreiberhau in the Giant Mountains of Lower Silesia. Many workers' sports groups from all over Europe gathered for the summer games in Frankfurt am Main between July 24 and 28, 1925. The photograph shows a group of athletes from the Ruhr area.
International Workers' Olympiad in Frankfurt 1925, black-and-white photograph, 1925, unknown photographer; source: Friedrich Ebert Foundation, Archive of Social Democracy, signature: 6/FOTB047354, https://www.fes.de/adsd50/arbeiterolympiade, non-commercial use.