If you look closely on the walls of the ruins, you will notice what appear to be old style fire pits. Light these with your torch. The wall will open up and you will gain access to a new room. One way will be a new exit to the swamplands. Two openings will lead you to rooms that have huge pedestals that must be lit with your torch. You must do these in the order as they appear one after another. They will lead you all over the island.