There are three big islands in the lake. The islands Lindau and Mainau are in the "Obersee". Reichenau is in the "Untersee". The Obersee is about long, from Bregenz to Bodman-Ludwigshafen. It is about wide at its widest point between Romanshorn and Friedrichshafen. The deepest point is deep, between Fischbach and Uttwil (just off Constance). 