In an age of rapidly rising fuel bills, the discovery of vast supplies of free hot water sounds too good to be true.
But that is exactly what one Dutch city has found to run the radiators of hundreds of homes, shops and offices.
Heerlen, in the southern province of Limburg, has created the first geothermal power station in the world, using water heated naturally in the deep shafts of old coal mines -- which once provided the southern Netherlands with thousands of jobs, but have been dormant since the 1970s.
Tapping "free energy" marks a breakthrough in green technology by exploiting the legacy of the coal mines that emitted so much pollution and helped to create the climate-change emergency faced by the planet.
"With the threat of global warming and soaring energy prices, nobody can afford to sit back," said Riet de Wit, a city councilman in Heerlen. "We have proven that a local initiative can provide a local solution for sustainable energy. Moreover, our concept can be adapted by former mining regions all over the world."