The Markelfinger Winkel is the part of

Lake Constance Lake Constance (, ) refers to three bodies of water on the Rhine at the northern foot of the Alps: Upper Lake Constance (''Obersee''), Lower Lake Constance (''Untersee''), and a connecting stretch of the Rhine, called the Seerhein (). These ...

between the upper part of the Mettnau Peninsula and Markelfingen. It is the northwestern continuation of the Gnadensee and its parent lake, the Untersee ("Lower Lake Constance"). It has an area of around one square kilometre.Bodensee: Teilseen und Rheinmündung
(map)

References

Geography of Lake Constance {{Konstanz-geo-stub