[Raphmedia]

The great north (both Canada and Russia) is covered with lakes and craters. It would be pretty hard to single out the caves from those.

Canada: https://www.google.com/maps/@60.1004328,-75.3335854,34459m/d...

Russia: https://www.google.com/maps/@72.0373772,97.0176475,62191m/da...