The Éperlecques blockhouse, a massive concrete fortress in the Pas-de-Calais region near Saint-Omer, was built by Nazi Germany during World War II with the goal of launching up to 36 V2 missiles daily toward London. Located 177 kilometers from the British capital, the site was chosen for its strategic position and natural landscape, which offered protection from British naval artillery. This structure was part of a broader military project called "Kraftwerk Nord West" and was constructed using 200,000 tons of concrete and 20,000 tons of steel. Much of the labor was forced, including prisoners of war, concentration camp detainees, and French conscripts. Construction of the blockhouse started in March 1943 and lasted until July 1944. The design used a unique method known as the "turtle method," where a massive 5-meter-thick concrete slab, weighing 37,000 tons, was poured at ground level and then gradually raised as the interior was built. The blockhouse was one of the largest in northern France, spanning 92 meters in width and 28 meters in height, with walls up to 7 meters thick in some areas. A similar structure, the Éperlecques Coupole at Wizernes, featured a massive dome made of 55,000 tons of concrete, 5 meters thick, and 71 meters in diameter. In July 1944, the British launched an attack on the blockhouse using a 5.4-ton Tallboy bomb, designed by Barnes Wallis. This bomb was specifically engineered to penetrate deep into large structures. The bomb struck the blockhouse through an opening, damaging internal equipment without penetrating the main concrete slab. This attack prompted Hitler to halt the use of fixed launch sites on July 18, 1944, as they were considered too vulnerable to such weapons. The liquid oxygen production equipment, essential for the V2 missiles, was later dismantled and sent back to Germany. The Éperlecques blockhouse was captured by Canadian troops on September 4, 1944, after the Germans had removed water drainage pumps to render the site inaccessible. In February 1945, the Allies tested a new bomb called Disney on the blockhouse, turning it into a testing ground for new methods of attacking concrete structures. Despite its impressive size and construction, the blockhouse never launched a single V2 missile. All 3,000 V2s aimed at London were launched from mobile sites instead. Today, the Éperlecques blockhouse stands as a significant historical site and a popular stop on memory tourism routes in northern France. The nearby Éperlecques Coupole has been converted into a museum dedicated to the history of rockets and space exploration. The blockhouse remains a symbol of how even the most formidable defenses could be overcome by innovative military technology.