Beneath this rusted metal cap lies the deepest hole in the world, tunneling for miles down into the Earth. The Earth is still quite a mystery to us, and we know more about certain galaxies than we do about what lies beneath our feet. That's why Soviet scientists in the 1970s decided to probe further than humanity ever has. They've been drilling off and on for nearly 24 years into the Earth's crust.
The resulting hole, the Kola Superdeep Borehole, has a drill depth of over 7.5 miles. That's further than the deepest known point of the ocean (which sits at about 6.8 miles down). So, what did we learn from digging so deep?
Well, at 4.3 miles down, the researchers found single-celled organisms and water. The temperature at the bottom of the hole is a blistering 356 degrees Fahrenheit. At this point, it became too hot to continue drilling, and the project was stopped in 1994.
The craziest part is that scientists estimate that the center of the Earth is probably around 4,000 miles down. The Kola Superdeep Borehole, at just 7.5 miles down, hardly even scratches the surface! Check out the video below to learn more.