The outer fortifications of the Küstrin fortress: Zorndorf, Säpzig, Tschernow and Gorgast. The rapid development of artillery technology in the 19th century forced the old "Feste Cüstrin" to be reinforced with external works. Since she was no longer able to protect herself. The Küstrin fortress secured the passage on the Oder and in 1872 was one of the most important German fortifications. Fort Zorndorf was built from 1883 to 1887 from 28 million double-fired bricks. It was the last unit fort of the Biehler type built in the German Reich.