On the Vélodyssée, on a small bike-less break, explore the Domaine de Certes-Graveyron. This 530 hectare property, owned by le Conservatoire du Littoral, is on some former dammed salt marshes. Nowadays, it’s a protected site that lets you discover some remarkable flora and fauna. Château de Certes is a beautiful chartreuse constructed by the Marquis de Civrac, and is currently undergoing restoration work.