3. Mariana Trench - The Darkest Depths
https://www.youtube.com/watch?v=6N4xmNGeCVU The Mariana Trench is famous as the deepest point in the world's oceans. It reaches a maximum known depth of 10,994 m at which point the pressure is so great that the water is nearl 5% more dense than at the surface (doesn't sound like much until you remember that water is supposed to be incompressible), and would crush you like a tin can. Despite being the deepest point in the ocean, it's not actually the point that's closest to the centre of the Earth, as the Earth is not a perfect sphere. It is still, however, pretty fricking deep. Despite the crushing oblivion, there's actually a fair bit of life down there from what we've managed to glimpse, again, mostly scuttly things. An some kind of ancient sea beast of course. Speaking of which, we'd better hope that the Mariana Trench isn't actually home to Cthulu, as some are considering it as a good place to dump all of that troublesome nuclear waste we've been generating. It is hoped that the movements of tectonic plates would eventually push the waste deep into the Earth's mantle. That would certainly make the problem go away, but whilst running the risk of poisoning anything that lives down there, small and scuttly and big and monster-y alike.