This is the one I'm using as my main, and just from this cave system alone I've found five stacks of coal (even now that I ignore most of it), five stacks of iron, a stack of gold and twenty diamonds. I'm nowhere NEAR finished exploring it.
The entrance looks inconspicuous enough.
This is one of two entrances that meet underground, branch off again, and meet again. In one of the lower branches there is a lava spill that ends where the two meet again, and just before the cave branches out again.
Just in the upper area, above where the lava spill ends, I found an iron block and nearly two stacks of coal. in the lower area, off to the left, there are two more branches: the rightmost one contains an epic amount of iron, at least two stacks, possibly three. The left one is even more remarkable- it leads to an extremely large cavern system, filled with lava, at just the right height for diamonds to be generated.
Again, the seed is "archimedes", and the coordinates for the entrance are in that pic. In fact, the only thing wrong with those coordinates as a location for a main base is the lack of trees- make sure you bring a few saplings to plant.
The entrance looks inconspicuous enough.
This is one of two entrances that meet underground, branch off again, and meet again. In one of the lower branches there is a lava spill that ends where the two meet again, and just before the cave branches out again.
Just in the upper area, above where the lava spill ends, I found an iron block and nearly two stacks of coal. in the lower area, off to the left, there are two more branches: the rightmost one contains an epic amount of iron, at least two stacks, possibly three. The left one is even more remarkable- it leads to an extremely large cavern system, filled with lava, at just the right height for diamonds to be generated.
Again, the seed is "archimedes", and the coordinates for the entrance are in that pic. In fact, the only thing wrong with those coordinates as a location for a main base is the lack of trees- make sure you bring a few saplings to plant.