The Geothermal Plant is a standard tile improvement in Civilization VI: Gathering Storm. It is used to supply Power to the city from a renewable source: Geothermal Fissure tiles, on which it must be built.
The Geothermal Plant is the second renewable Power supplier which becomes available after the Hydroelectric Dam, and the most powerful among the Power-supplying tile improvements. Unfortunately, it may only be constructed on a special terrain feature: the Geothermal Fissure. These are quite rare, and are usually found next to Mountains, Volcanoes, and near continent splits. Since this improvement is the only one that can improve this specific terrain feature, its use should be a no-brainer in most situations.
Just beneath the surface of the earth lies a form of sustainable, cost-effective thermal energy. Always available, the heat rising from the core of the planet has been enjoyed by people for thousands of years, often in the form of relaxing hot springs. But harnessing the energy of the earth to use as power is a relatively new practice. The world's first geothermal plant was built in Italy in 1911, and the second in 1958. Today, 24 countries are generating power through geothermal plants.
These plants are often found near tectonic boundaries, reducing the depth of drilling required to reach significant resources, but come with the risks of volcanic activity. Additionally, the plants create a side product – fluids containing gasses or toxic chemicals. While modern plants return most of these fluids to the earth to reduce environmental impact, some escape as steam, wafting through the air as the pungent sulfuric scent of rotten eggs.