The Löwentor (Lion Gate) is the impressive, crenellated gate of the disbanded Prussian fortress of Kaiser Alexander. The griffins on both sides of the portal, cast in the Sayner Hütte, and the large inscription give a good impression of the military and urban impression of the complex. To defend the city against enemies from the southwest, construction of the Feste Kaiser Alexander, one of the largest single fortifications in Germany, began in 1817. The fortress had an almost square ground plan with sides about 500 metres long on an area of 25 hectares. In addition to the surviving Fort Großfürst Konstantin and the battery on the Hüberling, the Alexander system included the vanished works of the Großfürst Alexander redoubt, Mosel battery, Moselweiss redoubt and the underground communication to Fort Konstantin. During the Franco-Prussian War of 1870/71, the fortress housed a prisoner-of-war camp for up to 10,000 men. In spite of great expenditure of funds, it had to be abandoned in 1903 because it was outdated and damaged by groundwater. After the First World War, the fort was almost completely demolished in 1920-22; only the Löwentor (Lion's Gate) and the Reduit remained. Battery Hüberling was given to the city of Koblenz before 1903 and is now a memorial. Various subsequent uses were discussed for the fortress, but none of these plans came to fruition. After 1945, slum quarters were set up in the Reduit, which, as in many other fortifications, were destroyed by demolition in 1964. Even today, the street layout on the Karthause is determined by the former ramparts and the Löwentor (Lion's Gate) greets every visitor on the way up.