Mariana Trench, Pacific Ocean
Just two humans have ever descended into the Mariana Trench’s deepest depths — aka Challenger Deep — and no-one has been there since 1960. Danger lurks in the perpetual darkness, a place where the immense pressure is crushing, and so great are the risks involved, it has become a no-go zone for even the most courageous.
But how vast is it down there, in the deepest natural trench on Earth? 1,500 miles long and 43 miles wide, Challenger Deep is almost seven miles from the surface.
To put it into perspective, imagine dropping Mount Everest into the gaping chasm. To do so would be to leave its peak still more than a mile under water. It’s hostile and unwelcoming, home to mysterious creatures that lurk in unseen places and it couldn’t be more difficult to reach. Forbidden? It’s hard to imagine a more foreboding location on Earth than this.