if ur sure u prayed at 3 stones, then u shud be ok <img src="/images/graemlins/smile.gif" alt="" />
the tower is located in the south section of the plains, on the right of the screen, against the edge. it quite dark and looks all destroyed and stuf!
oh, if u still can't find it, go right to the start of the south section and look for the cactaur ghost-he'll lead u to the tower, but u don't have to do this <img src="/images/graemlins/laugh.gif" alt="" />
and remember to press square again at the tower