Sonnenuntergang am Steinhuder Meer. Das Steinhuder Meer is a large lake in Niedersachsen (Lower Saxony), Northern Germany, located 30 km northwest of the state capital Hannover. It has an area of 30 square km, making it the largest lake of northwestern Germany, but it is very shallow, with an average depth of only 1.35 m and a max depth of less than 3 m. It lies within a region known as the Hanoverian Moor Geest. The lake has 2 islands: Wilhelmstein off Hagenburg was built in the 1700s and first served as a military fortress and military school, then a state prison. Die Badeinsel Steinhude was built in 1975 and has a sandy beach which is popular with summer guests. It’s accessible via an 80m pedestrian bridge from Steinhude.