This work, written in an understandable way for the interested layperson, introduces into the unknown world of the CO 2 gas volcanoes, the so-called mofettes. A little explored world that lets animals die in the middle of Europe, changes the flora, influences soils and the atmosphere and can provide clues for upcoming volcanic eruptions. With the help of the botanical bioindication, such degassing points can also be found in the field and even used economically, e.g. in mineral water and fire extinguishers, for the preservation of food and for the healing of heart and skin diseases. In this biological-geological mofette guide, Prof. Hardy Pfanz explains where such phenomena can be found in Germany, but also worldwide, and what they tell us. He also reveals - with a wink - one or the other extraordinary and legendary thing about mofettes.