Hallwilersee lies in Kanton Aargau and Luzern (1/6th of the area). It is a great place to visit. In spring you might be surprised by the red shores, caused by some algae (Burgunderblutalge), giving the lake a different look (I took another photo of that). Here, I went to the northern shore, where you have – if the sight is clear – a nice view to the alps across the lake. On this special day, the calm lake and nice clouds created a serene mood.