Ruskeala failure - is in Karelia, a huge hole in the ground somewhere at a depth of 10 meters - the water, the darkness ...
According to the recollections of local residents, the failure was formed in the sixties of the last century, after powerful explosions in a nearby quarry. The roof of the old waterlogged tunnels broke and fell into the water. On the surface, opened an impressive oval hole about 20 by 30 metrov.Ono leads approximately in the center of development, the perimeter of which today can be estimated at about half a kilometer. This underground area was rounded dry galleries associated with the main part of the current mining fleet, but they are now covered rubble.
The main feature of failure - a special microclimate. Due to the effect of cold ice bag in distant parts of the development does not melt ever. On it you can walk with caution, even in summer. Another thing - the very place of the failure.
In winter it accumulates through the cold, but the summer warm air melt and rain water gradually melt lake shaped repeating inlet.
Since June, researchers must first go down the rope in a rubber boat, and then disembark with her on the ice to melt.
For the experienced cavers plummet depth of 12 meters is not a serious obstacle, but in combination with water and ice, this descent can pretty tickle. To test this is not easy, but interesting.