Well, I’m working on my game and have almost reached a point where the programming is over, and the hard work begins.
In less than a month (I’m guessing) it will be level-building time.
My game is set mostly in caverns, or mines (as it’s base game descent was set in).
Now I am not a fantastic modeller of this sort of stuff, and was wondering if anyone had some tips?
You could try using cylinders, join them together and use subdivide with fractal,
then if you need to you could use proportional editing to make it a little more realistic
here is an example, sorry if its not the best 
Tunnel.blend (479 KB)
A tip I saw (but I can’t find to link to) suggested using metaballs (in this case the resolution would have to be low) and playing with them as they organically blend together (excuse the pun).
@Rapidbutton Brilliant, hadn’t thought of that at all
@Rubbernuke. Also a great idea.
In fact, with some experimentation, using metaballs for the outline, and then fractal subdividing for roughness gives an awesome result in short time. Thanks very much.