Owińska was the location of a mental hospital where approximately 1,000 patients were murdered by Nazi Germany during World War II. They were shot in the back of the neck in the nearby forest. The victims were buried in 28 mass graves. In the second stage of the same "aktion" conducted after October 26, 1939, the remaining patients were taken to a bunker in Fort VII and gassed with carbon monoxide released from steel bottles. A year later, additional 200 patients from Poznań were brought in and gassed at the same location.