These two lakes are in fact former valleys which were partially filled with salt water from the tides. The monks of the Benedictine monastery improved the access of water in the Middle Ages by deepening the canal entrance. As a result they are now flooded permanently. Bathers appreciate the water, two or three degrees warmer than that of the sea and with therapeutic virtues for those suffering from rheumatism and skin disorders. The path on the south bank commands splendid views of the hillsides.