Thanks. The "approach from the north" part helped. There is no tell-tale fungus to help you identify that it's a secret passage. I never would have found it otherwise. Thanks Edgwyn!
I hope Iisha can help me. I'm playing the ipad version of Escape from the Pit, on an iPad mini, which sometime makes hidden things difficult to find. I've wandered around the Sulfur Caverns in circles looking for the Cloak of Bolts book. I saw on some old maps that there is a lava lake near the river that's supposed to have some islands that you have to Orb on to. I've found the lake, but in this version there are no islands there. Help! What am I doing wrong?