Wells of up to a mile deep or more are drilled into underground reservoirs to tap into the geothermal resources in order to drive turbines linked to electricity generators. The first recorded instance of geothermal heat being used for producing electricity was in Larderello, Italy in 1904, although geothermal heat has been used for bathing since the Palaeolithic Age. Monkeys in Japan have also been shown to use heated water from hot springs to keep warm during winter months in mountainous regions.