In the city of Berezniki of the Perm region, Russia, there have already happened four soil collapses.
The first one shocked the city in 2006, the second appeared in 2007 and it was not the last one...
During the last collapse several heavy machines and one person went underground.
Currently they are trying to fill the holes with sand and gravel. More then 300 thousand of the material has been spent on it and it's not the end.
The same place after the filling.