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 Calidae, Algeria has shown the abundance of evidences about Aquae Calidae Christian past. Occupied by the Vandals in the fifth century and damaged, the city was recovered to "Romanitas" by the Byzantines and regained importance during the sixth century. Conquered by Arabs around 700 AD, Aquae Calidae nearly disappeared in the next two centuries. Aquae Calidae, Algeria Aquae Calidae was a Roman colony of the Roman province of Mauretania Caesariensis. The Roman city has been identified with ruins at Hammam Righa in the wilaya of Chlef, Algeria, North Africa. The ruins are located at latitude 36.379474N, longitude 2.395618E near the railway town