Description La petite Suisse du Nord (Small Switzerland of the North) named for it’s deep chalk valleys is a triangle of land between Calais, Boulogne and St Omer now promoted as Parc naturel regional des Caps et Marais D’opale. The 25-kilometre coast has several small ports including Ambletruse and is famed for tourism and fishing. Inland round Elinghen there was a small and now defunct coalfield as well as marble and aggregate quarries. Farming is cereal and sugar beet with forestry on the high ground. Réseau de la Petite Suisse du Nord (Network of the Small Switzerland of the North) a single track mainline from Amberleteuse to a junction at Ruminghem with the SNCF (French National Railway) Paris-Calais Line following the Slack, Crembreux, and Hem Valleys. The railway was built to develop Amberleteuse as a harbour and up market resort and with a junction at Elinghen to the Tramway de Crembreux giving access the coalfield, marble and aggregate quarries. The 500-meter tunnel under the Bois de Acquettes linking the Crembreux and Hem Valleys being the only significant civil engineering work. Audresselles the terminus of a continuation of the Réseau de la petite Suisse du Nord (Network of the Small Switzerland of the North) from Ambletruse Plarge built to develop tourism, industry and farming along coast. Set in the prosperous 1950’s to mid 1960’s the line was served by a frequent train service. Short trains provide the local passenger service. But the summer especially August brings tourist traffic with large engines hauling long Express and Direct trains making multiple stops at short platforms. Freight is active serving several quarries, shipping coal from the quay at Audresselles to the Tram de la Frenesie, and general freight. In practice the SNCF mainline line from Calais to Boulogne, recently electrified, passes through Elinghen with a connection at Caffiers to the Tramway de Marquise that runs to quarries in the Crembreux Valley.