If I dig a very deep hole, where I go to stop?

If I dig a very deep hole, where I go to stop? This is something I needed as a kid. Remember digging holes at the beach, and wondering whether you could “dig right through to China”. Well, if you dig straight down from Robe, South Australia, you end up in…the middle of the ocean. Oh well. Nice idea while it lasted. Won’t be able to pull the wool over little Jack’s eyes in the future…