There is a massive sinkhole near Solikamsk, Russia, in the Ural Mountains, that is now 120 m wide and 76 m deep. The sinkhole is located in a potash mine and began to develop in November of 2014. Potash is a general term for salts that are high in water-soluble potassium.
Local authorities believe that the sinkhole was originally caused by a flood in the underground mine. So far, the sinkhole has swallowed 20 homes and there are still more homes at risk.
The mine responsible for the sinkhole was owned by Uralkali, the largest potash producer in the world. They have since closed down the mine.
Click here to see the sinkhole documented in a BBC report.