The largest construction project of the Empire: Between 1886 and 1895, thousands of workers and hundreds of machines dug a 100-kilometer-long, 65-meter-wide, and 9-meter-deep canal through Schleswig-Holstein. The history of the North Sea-Baltic Sea Canal is told as a multitude and transformation of its meanings over time. The historiographically multifaceted, non-linear approach is already reflected in the duality of the title; it refers both to 'the' great excavation, meaning the construction of the canal, involving engineers, workers, and machines, and to 'the' great ditch, meaning the canal as a project, as an object of expectations and fears, of publications and politics, and as a consequential intervention in a landscape and a habitat for people, animals, and plants. In this context, the canal also symbolizes the connection and division of European nations: its prehistory.