Credit to Sirynia and Desarii.

From Icewall port: 6n, up, 3e
You can enter the stream to get to the Underground Lake, to get out of the Lake you enter a hole which leads you do the Large Cavern



                           A Long---------A			
                           Tunnel-------Cavern	   A Underground		
	                  /	    (enter stream)----->Lake
		         /			    (enter hole)
                        /                            /
		       /                            /
		 A Large-------A-------------A Large-------A Natural 
		  Cave-------Tunnel-----------Cavern--------Cavern
               (entrance)
		       \
		        \
			 A---------------A		
		         Tunnel-------Cavern
				   (enter stream)----->A Deep
						        Hole	
					      (must recall to get out?)