Biggest goddamn cave system I've ever seen, but totally devoid of anything but iron and redstone (and tiny bit of gold). Finally found four diamonds. Blown into lava by a creeper peeking over my shoulder.
I didn't lose anything else of real value though. I'm just amazed by this cave system.
You have no idea how insane these cave systems can get.... I got sick of exploring mine. They never end. I am starting to assume that every underground cave is connected to each other. I have to bring signs with me to avoid getting lost. Thought it was just the spot I was on, moved about 2 miles away..... more caves.
UPDATE: I have finished my town hall basic layout, rooms not yet added, (if someone gives me awesomely detailed (super noob here) instructions on posting pictures because my previous attempts have failed then I will post pics.) and completed the first phase of my railroad system from my main fort to my empty town of loneliness. The first phase includes 3 parallel railways and 2 station layouts. They stretch for who knows how long and I have so far used >3000 wood. Now all I need to do is add supports just for the hell of it, fix up the stations, remove the dirt and series of bunkers used to be safe for the night, and add what I assume to be ~500 railroad tracks, which means I need 180 iron bars.