404
Seed: 404
So you’re up for a challenge? Well I really hope you are, because what lies ahead is one of the most treacherous naturally generated minecraft seeds of all time. Known as the “404 challenge” this seed became well known because of the huge cave you enter by falling down along with a ton of Gravel. unfortunately the rest of the world is not very interesting.
You will spawn in an area hopefully near a large body of water. Make your way to a large patch of gravel that looks like the picture below. Prepare yourself (you have until nightfall to gather your required materials), and then dig the gravel to descend.