80 years ago, Isle Crémieu was covered under hundreds of meters of ice and must have looked like Alaska today. The Isère glacier stayed like this for several tens of thousands of years and retreated only 000 years ago.

The passage of the glacier reshaped the landscape by alternating over-digging and depositing of materials. During its melting, the basins became waterproof and gave way to lakes. For several thousand years, these filled in, forming large areas of marshes (peat bogs).

Save Lake is a relic of these post-glacial lakes. With a depth of 15 meters and steep banks, its morphology bears witness to the deepening of the glacier. It too is destined to fill up, its peat banks will gradually advance and reduce the open water surface. It is impossible to realize the phenomenon on the scale of a human life: it would take around 15 years for the lake to become a marsh!