The Passage du Gois is a natural causeway that connects the island of Noirmoutier with the mainland of France. The causeway is a unique geological formation that is only accessible during low tide, as it is completely submerged during high tide. It stretches for 4.3 kilometers and is made up of sedimentary rocks and sand, and is an important tidal flat ecosystem. The passage is often used by pedestrians, cyclists, and motorists alike, and is a popular tourist attraction due to its unique nature.

The Passage du Gois has a rich history, dating back to ancient times. It was used as a salt route during the Gallo-Roman era, and in the Middle Ages, it was a strategic point for pirates and smugglers. Today, the causeway is well-maintained and is open to the public during low tide, with a schedule posted at the entrance to the causeway indicating when it is safe to cross. Visitors can take a leisurely walk across the causeway and enjoy the stunning views of the surrounding marshlands and sea. The Passage du Gois is also a popular spot for fishing, as a variety of fish and shellfish can be found in the tidal pools