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Heritage classified

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Origin and history

The Dike du Large is a major maritime structure built between the 18th and 19th centuries to protect the harbour of Cherbourg-en-Cotentin, in the English Channel. Designed in 1776 under Louis XVI to secure a military port capable of sheltering 80 warships, its construction began in 1783. Louis-Alexandre de Cessart's initial project, based on 90 wooden cones filled with stones, failed in the face of storms. After interruptions linked to the Revolution, the work resumed in 1802 under Napoleon I, according to the method of The Bretonnière, combining rocking and squashing of old ships. The central dike was completed in 1853, while the eastern and western dikes were completed in 1895, forming a set of more than 6 km.

The 3,640 m long, 100 m wide at its base and 27 m high, is equipped with three forts (Central, East, West) and incorporates navigable passages from 700 to 1,100 m wide. It symbolizes the French strategic ambition against England, notably under Napoleon I, which makes it a key port for a possible invasion. The work, marked by technical innovations and logistical challenges (such as the transport of stones from the Becquet port), spans more than 70 years, involving engineers like Joseph Cachin. The dam resists German destruction in 1944 and remains an exceptional testimony of port engineering.

The Cherbourg harbour, the second largest in the world after Ras Laffan (Qatar), plays a crucial military and commercial role. It hosts historical events, such as Queen Victoria's visit in 1858 or the Titanic stopover in 1912. The strong associates, such as those of Pelee Island, Querqueville and the Flemish, reinforce his defence. Ranked historic monuments in 2021, these works illustrate the evolution of military techniques, from the 18th century (casematized battles) to the 19th century (castoning and modern artillery). The dam and its forts, now partially open to the public, embody a unique maritime and strategic heritage.

Among the notable anecdotes, the dam is linked to accidents, such as the drowning of astronomer Charles-Eugène Delaunay in 1872 or the collision of the Kaiser Wilhelm der Grosse in 1906. It is also the scene of naval demonstrations, such as the presidential review of 1933 with the Vauban counter-torpedo. The forts, such as Pelee Island (transformed into a prison during the Revolution) or Querqueville (sold to privates in 2013), tell a complex story, between technical innovations, political issues and military adaptations. Their recent preservation, through inscriptions to historical monuments, underscores their heritage value.

The construction of the dam reflects the geopolitical tensions of the time, from the French naval defeats (such as the Battle of the Hougue in 1692, where the Sun Royal dark) to the Napoleonic projects. The debates between engineers (Cessart vs. The Bretoner) and the technical choices (masoned boxes, ripples) show a constant quest for efficiency. The dam, designed to withstand maritime assaults, also became a symbol of resilience: spared in 1944, it remained a landmark for navigators, with its 25-metre lighthouse on Pelee Island. His legacy continues, between military memory and tourist attraction.

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