Oiseaux du Lac de Grand-Lieu - Site de Pierre-Aigüe

In winter, it is the largest natural plain lake in France; its surface varies from 6,300 ha in winter to 2,300 ha in summer. 2,700 ha are classified as a National Natural Reserve and 650 ha as a Regional Natural Reserve, which notably prohibits hunting and public access on the lake.

The Grand-Lieu Lake, characterized by exceptional biodiversity, is primarily renowned for its rich ornithological wealth, with over 300 bird species (including rare ones).

There are some structures and sites allowing information and observation of the lake's surroundings, particularly in Passay, the lake's fishing village. For centuries, fishing was the main activity of this village; today, only 7 professional fishermen are authorized to continue this activity.