Between Granville and Cancale, the bay of Mont-Saint-Michel forms a 193 sq. miles (500 km²) low-lying area, home to the highest tides in Europe. The most spectacular ones follow the full and new moons. In the event of a very strong tide, there can be a difference of more than fourteen metres between the low and high sea levels (the tidal range). The bay then reveals all its secrets: the fauna, the flora, the lights, the reflections... But the bay can be dangerous. To cross it by foot, it is strongly advised to go with a guide.