Île Longue is a peninsula on the commune of Crozon, attached to the Crozon peninsula. its altitude is 42 metres and has an area of 1.10 km2. To the north of the peninsula there are two small islands: Ile des Morts and Ile Trébéron. Originally the isthmus was a mere sand bank, and crossing was only possible at low tide. During the 19th century, it was improved with a stone pathway. During the construction of the strategic base (1967–1972), it was widened, made insubmersible, and changed into a big parking space.