This road that goes along the bottom of Burnef bay connects Noirmoutier island with the continental part of France, and it is just unique. Two times a day something unimaginable happens there. Passage du Gua road regularly goes under water. It is relatively dry and available for transportation only around 2 hours per day. For the rest of the day it becomes a part of the sea bottom at 4 m depth.
Oh, and its length is 4,5 km. It doesn't seem that long, however, it is very dangerous. There are special signs with tide schedules along the road. But despite of that many people get stuck there every day. For those lucky ones there are several towers where they can wait for the water to go down, but then, of course, they can forget about their cars.
The road was discovered in 1701.
It is odd but, despite of the fact that this road is under water most of the time, it doesn't get destroyed.