Yes, go to the gnomish airport (IF Airport...w/e you call it xD) there is a guide somewhere on this site. Ok you wanna go the the glitched dwarf who looks to be using a hammer...(>.>

and use a noggenfogger for lightfall or a mage for slowfall. Whichever. then jump down the cliff. You'll eventually land (after some self explanitory jumps I might add) in a "dwarven farm" as its called. Explore there for abit and you'll eventually find a tunnel, thats the tunnel your looking for. I've actually seen a vid where if aimed correctly you could "swim" under IF and then go up into it from the ground. Never managed to get the jump right or even know if it really works. But hey it was fun trying

if thats not clear please tell me.