the region was known from ancient times for its volcanic nature and for the very hot springs. the romans used its sulphur springs for bathing. in 1827, françois de larderel, a frenchman, invented a way of extracting boric acid from the volcanic mud by using steam to separate the two. the town larderello has the name in honour of larderel's work. the region was the site of a pioneering experiment in the production of energy from geothermal sources in 1904. prince piero ginori conti tested the first geothermal power generator on 4 july 1904, at the larderello dry steam field in italy. it was a small generator that lit four light bulbs. later, in 1911, the world's first geothermal power plant was built there. in 1911, the world's first geothermal power plant was built in the valle del diavolo ("devil's valley"), named for the boiling water in the area. larderello now produces 10% of the world's entire supply of geothermal electricity, amounting to 4,800 gwh per year.