I'll have to go over and check out the area you're talking about, but I don't think it's the same place. It's probably actually small to you pro-spelunkers, but it's the biggest cave I've found to this point. What was happening is I'd reach the end to what I thought was the area and lo and behold, there's a shaft up that leads to another mess of cave. Also, when I tunneled up I ended up in the middle of Fight Isle, so I think that's north of where yous guys are.
Pretty stoked for the new rail types coming in the next patch. There's powered, non-powered, and then detector rails. The detector rails mean when a car passes over them, they send out a red stone signal. So I guess you can make mechanical shit happen. (Search youtube for videos of the piston mod- people have already made insane-ass Rube Goldberg machines.) The specialty rails are made from gold also, so that's a neat twist.
You should join in, Ryan! Oh, and Mike can do his digs in MC like he did in the quake engine :) What's Johnny been up to? He must think our posts are insane.