I am currently digging a vertical tunnel to hell, making sure to drain any ponds, lakes, or other watery spaces into nearby caverns.
Julie drops by every so often with more wood, so that I can make platforms to get myself back to the surface.
Yup, the ridiculously enormous
Terraria 1.2 patch came out a couple of days ago, so we've rekindled our addiction.
First fun thing we found: The new snow biome, including penguins!
Sadly, said penguins did not last long when night fell and the zombies attacked. But there always seem to be more of them, so that's probably fine :->
This is the digging so far:

You can see me at the bottom of the pit, Julie halfway down it. Our home (with villager we've adopted) is on ground level.
Same map, zoomed _all_ the way out. Clearly quite a bit to explore:
