Larderello is a geologically active area of southern Tuscany, Italy, which is renowned for its geothermal productivity. Located at , the region was known from ancient times for its volcanic nature and exceptionally hot springs. The Romans used its sulphur springs for bathing. During the 18th and 19th century, they were exploited to extract boric acid.

The region was the site of a pioneering experiment in geothermal energy production in 1904, when five light bulbs were lit by electricity produced through steam emerging from vents in the ground - the first ever practical demonstration of geothermal power. In 1911, the world's first geothermal power plant was built in the Valle del Diavolo ("Devil's Valley"), named for the boiling water that rises there. It was the world's only industrial producer of geothermal electricity until 1958, when New Zealand built a plant of its own.

Larderello now produces 10% of the world's entire supply of geothermal electricity, amounting to 4,800 GWh per year and powering about a million Italian households. Its geology makes it uniquely conducive to geothermal power production, with hot granite rocks lying near unusually close to the surface, producing steam as hot as 220 °C (396 °F). However, in recent years concerns have been expressed about the sustainability of its steam supply, as a 30% drop in steam pressure levels has been recorded from the maximum levels of the 1950s.

The region has experienced occasional phreatic volcanic eruptions, caused by explosive outbursts of steam trapped below the surface. It possesses about a dozen explosion craters 30-250 m in diameter. The largest is the Lago Vecchienna crater, now filled by a lake, which last erupted around 1282.

References

• Global Volcanism Program - Larderello
• "Steaming Forward", Time magazine, June 16, 2003