To facilitate the construction of the vast defenses on the island, a network of railway lines were established across it. These primarily transported the required amounts of material to the construction sites, but also the laborers to some extent. The depot established at L'Islet was one of the largest on the island, and contained running sheds, water cranes as well as workshops for repairs to the rolling stock which included pits. Stores of material were located at the northern end of the depot.
By March 1943, it was directly connected by railway lines to the yard on the northern side of St Sampsons harbour, at Les Monmains, and to Mont Crevelt where it then proceeded across Belle Greve to the White Rock. Lines also proceeded northwards, up to Fontenelle through the stonecrusher at Longree, L'Ancresse, and westwards following the back of the anti-tank wall. The line running south hugged the coast at least as far as Wn. Grüne Düne at Rocquaine Bay, and a section of concrete from this remains visible near the toilet block (although not in its original position).
As of today, the foundations of some ancillary buildings, perhaps workshops or stores, are visible but little else.