 It has an area of , a maximum length of about 3.4 kilometres and a maximum width of 1.6 kilometres.The lake is up to 38 metres deep, its surface elevation is about and it is crossed by the River Schwentine from east to west.This waterway links the Dieksee to the other lakes in the Holstein Lake District (the Kleiner- and Großer Eutiner See, the Kellersee, the Großen- and Kleinen Plöner See and the Ukleisee).