Happerschoss to Allner

Allner See is an artificial lake near Hennef in Rhein-Sieg-Kreis, North Rhine-Westphalia, Germany. At an elevation of 63,5 m, its surface area is 0.10 km². Directly to the north is the 15th century castle Schloss Allner.Starting in 1979 excavations to obtain sand and gravel for the construction of Highway 560 created a pit some six meters below the water table.