Alongside the Space Race, the mid-1900s saw another contest of engineering -- a race downward, into the Earth. Learn why the USSR created the Kola Superdeep Borehole (the deepest artificial or natural hole we know of), what we learned from it, and how this research continues in today's episode of BrainStuff, based on this article: https://science.howstuffworks.com/engineering/civil/kola-superdeep-borehole.htm