Mysterious Holes of Russia

This is another place which is one of the most mysterious places in the world. People has been finding strange holes in Russian forests, this strange phenomena has been occurring since the end of the 1980s. This strange phenomenon consists of strange and deep holes that appear suddenly in the dense forests, in those places that no truck or car can get to, let alone drill anything. If these holes are being digged, there is no soil around these holes that indicate that they have been drilled. People who have gone down these holes haven’t found anything, and there is no answer on how or why are these holes being used for.