The karst springs in the Bruchwiesen nature reserve

Bad Tennstedt lies on the edge of the Schlotheimer Grabenbruch. This means that not only surface water flows towards Bad Tennstedt, but also underground water. Coming from the Harz Mountains, the groundwater flows through layers of shell limestone and, in addition to loamy-clayey sediments of the lower Keuper, also layers containing gypsum. The water washes out the shell limestone and gypsum layers before it emerges as a spring. All three main springs in the Bruchwiesen area are therefore sinkhole springs. Their formation is related to the leaching of gypsum and limestone in the subsoil. As a result, the waters of the three main sources of the town of Bad Tennstedt - Brewery pond, Small and large glass hole and the Coachman's hole - has a very high degree of hardness.

In the spring funnels of the Gläserlöcher and the Bruchteich pond, the washed-out minerals create a unique play of colors. Due to the low nutrient content of the spring water, the water remains very clear and clean. The minerals dissolved in the water prevent the water from freezing even in the coldest winters.