was supplied by local concentration camps such as Neuengamme in Hamburg. Valentin: Hornisse: Hamburg The city was the site of two structures, "Elbe II" and "Fink II". The Finkenwerder bunker was constructed by 1,700 slave labourers over four years. After capture, it was demolished with 32 tonnes of bombs. Elbe II: Fink II: Helgoland The "Nordsee III" bunker in Helgoland was one of the oldest submarine pens, being started in 1940. It was left alone until near the end of the war when it was attacked by the RAF and like most of the facilities on the island, completely destroyed. It was also used after the end of the war for testing new weapons. No trace of the pen has survived. Kiel This town was constantly bombed in World War II, the targets often being the "Kilian" and "Konrad" bunkers. They were started in 1941 and 1942 respectively. The latter was used for the construction of Seehund midget submarines. It was in "Kilian" that was probably the only submarine to be lost in a bunker. Misguided bombs from an air raid on the town caused what might today be called a tsunami to cross the Förde and enter the bunker. Oberleutenant zur See Hans-Gerold Hauber, the captain of , had courted ridicule by ordering all hatches on his boat to be closed, despite being in the bunker. "This simple precaution saved U-170 from sinking while lying next to U-4708". Wilhelmshaven A U-boat bunker in Wilhelmshaven was planned, but it never got beyond the preliminary stage. France The German occupying forces built many U-boat pens in the Atlantic ports of France in Bordeaux, Brest, La Rochelle/La Pallice, Lorient, and St. Nazaire. Almost 4.4 million cubic metres of concrete were used. Bordeaux An unnamed bunker and bunkered lock were constructed in Bordeaux, the fourth largest French city at the start of the war. Both structures were started in 1941; the bunkered lock was not finished by war's end. The main building was larger than those in other locations; this was to allow supply boats and minelayers to use it. The Royal Italian Navy established the Betasom base at Bordeaux. The port was also the target of a British commando raid – the so-called Cockleshell Heroes. Brest The Brittany port only had one bunker, but it was the largest; it was also unnamed. Started in 1941, the plans were modified many times before