There is a place in Russia which is also called the gate of hell. It is the deepest borehole present in the world. This hole, called the Kola Superdeep was started in 1970 by scientists of Russia. To challenge the American scientists, they wanted to dig deeper, after 19 years of digging for 19 years, the scientists had reached 12 km deep, but only then did they have to stop the excavation.
According to the research, as scientist started digging in the depth of the ground, the temperature of the machine started increasing rapidly. When they reached the depth of 12262 meters, machines stopped working. At that time the ground temperature was 180 degrees Celsius. Then, the scientists named the hole as Door to Hell.
Excavation of 12 kilometers in the land is not less than any wonder in itself, but you will be surprised to know that it is not even 0.2 percent of the depth from surface to earth's core.