Lac de Sylans

It is significant for the ruins of one of the 19th century's largest ice harvesting factories and the occasional outflow of water in two directions.
The lac de Sylans fills part of the Nantua water gap, which was formed during the last glacial era. The formation of the lake itself is much more recent; it is the result of the collapse of the cliff on the Northern side of the valley a few centuries ago. This huge landslide partially blocked the valley between the ice factory and the source of the Doye, above les Neyrolles, blocking the river that was flowing along what is now the bed of the lake, causing the lake to form. Today the water percolates through the landslide debris to form the source of the Doye.

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