Sinkhole in Muschelkalk (shellbearing limestone) karst, between Bad Berka and Saalborn, Thuringia, Germany
<a href="//commons.wikimedia.org/wiki/User:KaiKemmann" title="User:KaiKemmann">KaiKemmann</a>
CC BY-SA 4.0
<span class="int-own-work" lang="en">Own work</span>