Sparkling wine in the ancient method (Method ancestrale) This is the first method in which sparkling wine was produced in a deliberate way. It is recorded for the first time in 1531 (long before Champagne). The method was developed by monks in the village of Limo in the south of France. The first fermentation is stopped by cooling the wine to a low temperature (at a precise stage in the fermentation), then the wine is bottled and then the fermentation continues in the bottle. 
The word "natural" refers to the fact that the fermentation takes place on  the wild yeast and that no sulfur has been added to the wine. In addition, no sugar was added as is done in the Champagne method.