This week, as temperatures dip to 12 °C at night and rise to 22 °C during the day, many households across France are turning on their heaters or stoves for the first time. In the village of Chaudes-Aigues, located in the Cantal region, however, some homes have never needed this seasonal ritual. The reason lies beneath their floors: hot water flows continuously from the ground at 82 °C, a phenomenon that has existed since the 14th century. This water comes from the Par spring, which flows at a steady rate of 500 liters per minute. According to a 2023 scientific communication by the BRGM (French geological survey), the Par spring is the hottest thermal spring in Europe. That rate translates to 720,000 liters of water per day—nearly 5,000 bathtubs of 150 liters each, all at a temperature too hot to use directly, day or night, year-round. The history of this unique resource dates back to 1332, when a local resident sold hot water from the spring to three neighbors, enabling them to heat their homes. This early system is considered the first urban heating network in France. It used wooden pipes, stretching about 5 kilometers, to distribute heat to around 150 houses by the 19th century. However, the wooden pipes had a drawback: mineral deposits, or scale, would accumulate over time, clogging the system. Maintaining the network was a shared responsibility among residents, who had to regularly clean their portion of the pipes, without the use of modern meters or energy bills. Today, only a few homes in Chaudes-Aigues still use this ancient system, relying on private springs for heating. While the commune does not provide the exact number of such homes, it is clear that the original network has significantly diminished. The village preserves the memory of this early heating system through the Géothermia museum, which showcases the history of the springs, the wooden pipes, and the people who once depended on them. Visitors can see the Par fountain, where steam rises from the 82 °C water, creating a visible plume that drifts into the narrow alleys when the air cools. Chaudes-Aigues offers a glimpse into an early form of geothermal energy and community resource-sharing, which predate modern heating systems and energy policies. While today's heating systems rely on distant energy sources, the residents of Chaudes-Aigues have long benefited from a natural resource that is already hot when it emerges from the ground. This contrast highlights the physical limits of heating systems: the water under the floors cools as it travels, requiring careful planning of the pipeline routes and regular maintenance. For visitors to the Cantal region in the fall, the Par fountain is a must-see, as the steam becomes most visible when the air cools, revealing the power of this natural spring.