In my first map I dug a long tunnelto the sea, added some minecart tracks and made stations partway through, i couldn't find enough iron for the tracks though...
I started a new game and found the greatest mine ever!
So much coal that I could cry, more iron than I saw in total in my last world, red ore practically jumping out in front of me, even a few diamonds and some gold. The floor looks like the mansion of an eccentric billionaire because of all the obsidian. I noly need to go up to the surface to get wood for torches and pickaxes...
An it's close to my spawn, I'm building a mine cart train line to there...