The Jeddo Tunnels a huge one, 9 miles of tunnel is 4 sections. the tunnel itseld is pretty big, 7' x 9'. the drainage tunnel is pretty low in elevation so alot of the workngs are above the minepool. its drains a huge area, over 30 square miles so there is alot of water coming out, even if you could get in there im not sure if i would want to, hazleton has been known to dump sewage and industrial waste into the old mine workings the past.
i dont have any pictures of this one but i found a study that was done on this tunnel, ill put the link below, it has some maps at the end of it.
http://www.srbc.net/jeddowaterbalance.pdf