The factory's location along the Chishui River ensures ideal moist conditions for the fermentation process. [Photo by Jiang Wanjuan/chinadaily.com.cn]

As a traditional Chinese condiment, soy sauce was invented by the Chinese over 2,000 years ago and is still used in Chinese cooking every day.

However, modern people tend not to give much thought to the making of soy sauce, as the traditional brewing method, or fermentation, has long been replaced by a chemical process, which is much more productive.

Little known to the outside world, a century-old factory in Xianshi town, Sichuan's Luzhou city, is still using the natural fermentation method to produce its products. That means simply exposing a soybean mixture in big jars to the sun, a method that takes up to three years to complete.