The mine tunnel I'm talking about goes out a long way North from the pumpkin mine (towards Eric/Rood territory).

I wouldn't be surprised at all if you are on the other end of the same cave system. It's frigging HUGE. I've never seen this much lava in one cave before. It's nuts.

I'm doing everything I can to not kill the lava. The other problem I'm running to is that when I'm digging around the lava lakes, I'm hitting underground rivers that are spilling out and creating obsidian. Thankfully, they haven't pushed me into the lava just yet, but it's been REALLY close a couple of times.

And, using F3, I can see a good dozen-plus baddies in the cave system very close by.