Canton of Glarus
Once a section of the Obersee area, the former easterly lake "Tuggen" was landed in the early 16th century AD and for the last time mentioned in 1535 AD. Parts of the former lake were situated in the Canton of Glarus, the larger western area in the canton of St. Gallen towards Uznach. In much earlier era, "Obersee" and "Tuggenersee" also were separated by the "Buechberg" hill, on those eastern side the Grynau Castle is situated.