The whole Marais Poitevin and Aiguillon Bay area represents about 100 000 hectares. Located on 3 departments (Vendée, Deux-Sèvres et Charente-Maritime) and 2 regions (Pays de la Loire et Poitou-Charentes).

The space left by he ocean day after day has been filled by sea and river alluvium. The result is a vast flat area with an intermediate altitude between low and high tides.

The dried marshes are 47 000 hectares wide. The wet marshes (the eastern part is called Green Venice) are 29 000 hectares wide. The intermediary marshes (which are imperfectly dried) are 19 000 hectares wide.

(source Wikipédia, translated)