Container-ships’ size as well as sea transport keeps expanding. As the result, ports of the Atlantic Coast are saturated. Our solution is to organize one mega-port off St-Nazaire coast functioning as a relay for the French Atlantic coast. Using 3D software as Rhinoceros, Grasshopper and 3DS Max we generated a huge city shaped as a hemicycle facing the uninterrupted container choreography. The architecture and urban typology is based on climatic conditions: the wind and the sea. City topology is made of several street levels with houses, looking like chrysalides, fixed to the vertical structure that bonds different streets layers.