The Marais Poitevin

The region formed by the marais poitevin marshlands and Aiguillon Bay (the remains of an old gulf) covers an area of around 100,000 hectares and straddles three départements: Vendée, Deux-Sèvres and Charente-Maritime.

Over time, the ocean receded and the region gradually silted up, forming a vast expanse of flat land with an altitude of between 0 and 8 metres - between high and low tide levels. The dry marshes cover an area of around 47,000 hectares. The wet marshes (the westernmost part of which is known as Venise Verte or Green Venice) cover an area of around 29,000 hectares, whilst what are known as the intermediate marshes (because they are not completely dry) make up an area of around 19,000 hectares.

The wet marshlands of the Venise Verte have been awarded the “Grande Site de France” label.

http://www.sudvendeetourisme.com/loisirs-et-decouvertes/embarcaderes-du-marais-poitevin/