This mysterious hole is located about 30 km from Bovanenkovo, Yamalsky District, Russia. Some speculate that this might be not a sinkhole after all, but a crater from an unknown meteor impact. Others think that this hole might be a result of an underground explosion.
Update: Some Russians think this is a pingo.
The mysterious sinkhole from inside. Scientists have visited the Yamal hole. They are still not sure what caused it.
– via r89.ru