Deepest Hole in the World.

I remember watching an episode of Oggy and Cockroaches where Oggy and The Cockroaches were in China and they had to run away from angry people who are chasing them. The four animals escaped from the angry mob by jumping into a long hole which leads to their hometown.
Surprisingly in reality, there is a hole digged in Russia during the 70's. I expected it to be a fast transport to various parts of the world. It somehow came to a halt due to scientific factors that are later explained in the video.