The confusing and maze like cave system is a very challenging map, and it is only suggested the most experienced STW players go in it.
The caves can be broken down into 4 levels
The first level
This is the level you are in when you first enter the map via the underground river. there isn't much to it other than the river.
The second level
This is the part you reach the first time you climb up out of the river, if you expected me to tell you how to get here, you are wrong. you can figure that out on your own. this isn't a walk through.
the third level
If you find your way up out of the second level then you are in the third level. this part is actually pretty straight forward, unless you make a wrong turn...
the fourth level
This is the most difficult part of the cave system. if you find dirt, then you are on the fourth level. there are lots of paths out of this level, but only 1 goes somewhere interesting.