Sommen is a Swedish lake. Its area is 132 km² and its greatest depth is 60 m.(although deeper places are found every year) The lake is located in southern Sweden, and is bounded by the provinces of Östergötland and Småland.The lake is a clear-water lake, with a visibility of 9–11 m in the eastern parts of the lake. This makes Sommen one of the greatest clear-water lakes in Sweden.According to tradition Sommen has 365 islands, one for each day of the year.