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
Free Imperial City of Aachen the Treaty of Lunéville, Aachen was incorporated in the French First Republic as chief town in the Roer department. Later, the Congress of Vienna gave Aachen to the Kingdom of Prussia. Free Imperial City of Aachen The Free Imperial City of Aachen, also known in English by its French name of Aix-la-Chapelle, was a Free Imperial City and spa of the Holy Roman Empire west of Cologne and southeast of the Low Countries, in the Lower Rhenish–Westphalian Circle. The pilgrimages, the Coronation of the Holy Roman Emperor, flourishing industries and the privileges conferred by various emperors made it one of