A Geothermal Fissure is a type of terrain feature in Civilization VI: Gathering Storm. It provides additional Science yield on top of the base terrain yield and can later be improved by a Geothermal Plant.
Geothermal Fissures are often found at the foot of Mountains and Volcanoes and present ideal locations for cities. Hungary's Thermal Baths provide additional Amenities and Tourism in a city with one or more Geothermal Fissures, and Campuses built next to them enjoy rich adjacency bonuses. Finally, with Synthetic Materials, Geothermal Plants can be built on them to provide a city with additional Science, Production, and clean Power.
On an Earth map, there will always be two Geothermal Fissures near Mount Kilimanjaro. Players who spawn in Africa should attempt to settle near them, especially if Science is an important part of their strategy.
Places where the Earth's crust is fractured enough to allow heat from deep underground to escape are geothermal vents. These can take the form of natural hot springs, geysers, or smokers which do not rise to the energetic levels of volcanoes. These have attracted people since antiquity, drawn by the unusual geology and the attraction of warm water for bathing and ritual.