The Severn Estuary is fringed by extensive areas of reclaimed alluvium, known as the Levels, which form a distinctive type of landscape. This work is a synthesis of evidence about how this landscape has evolved. Archaeological, palaeoenvironmental, documentary, cartographic, place and field-name evidence is drawn together to address key themes related to the exploitation of this physically marginal area. The central issue is how, when and why the countryside came into being. The study sets the Severn Estuary within the wider context of the British Isles and north western Europe, and focuses on the neglected Roman and later periods, and on areas of coastal alluvium.