Location: Russia
Year Discovered: 1900
Est. Value: N/A
What is the Earth’s center made of? Scientists in Russia have been working for decades to find the solution, drilling a 40,000-foot-deep hole into a desolate peninsula.
However, a curious occurrence during the excavation compelled the experts to quickly and discretely plug the hole.
As the scientists dug, temperatures sharply increased, reaching 356 degrees Fahrenheit. The Russian crew realized they had to give up the project since the granite was so soft and may potentially damage their tools. In 1995, the Kola Superdeep Borehole was formally closed.