Grauerort fortress - Credit: Wikimedia Commons
Grauerort fortress - Credit: Wikimedia Commons
Grauerort fortress is a German artillery fort on Elbe river about 9 km (5.6 mi) north of Stade which was built between 1869 and 1879 to defend the Port of Hamburg. Its shape is hexagonal, taking advantage of the topography of the area and the location of the previously existing levee. The main armament of the fort were probably ten 21 cm breech-loading guns (as opposed to the initially planned four 28 cm and six 21 cm guns), but they are no longer in place. There were also 4 12 cm and six 9 cm guns. Construction materials were cement and brick; concrete was only used from 1885 onward. Read more on Wikipedia
Source: en.wikipedia.org