Geothermal heating a total capacity of 15 GW extracted 88 PJ of heat energy for space heating. Global ground-source heat pump capacity is growing by 10% annually. Hot springs have been used for bathing at least since Paleolithic times. The oldest known spa is a stone pool on China's Mount Li built in the Qin dynasty in the 3rd century BC, at the same site where the Huaqing Chi palace was later built. Geothermal energy supplied channeled district heating for baths and houses in Pompeii around 0 AD. In the first century AD, Romans conquered Aquae Sulis in England and used the
Aquae Sulis crossing point of their road, they would have been attracted by the large natural hot spring which had been a shrine of the Celtic Brythons, dedicated to their goddess, Sulis. This spring is a natural mineral spring found in the valley of the Avon River in Southwest England, it is the only spring in Britain officially designated as hot. The name is Latin for "the waters of Sulis." The Romans identified the goddess with their goddess Minerva and encouraged her worship. The similarities between Minerva and Sulis helped the Celts adapt to Roman culture. The spring was built up into