Originally posted by Zlandicae:

Hi.
Short question: Do you think it will ever be possible to dig real caves in the game? :)

Unfortunately no, unless they re-do the terrain system. The closest we'll be able to do is dig under a boulder or unattached terrain feature (such as boss summoning platform) to create a small "cave" but other than that whatever we do we'll have to build our own roof above it.