From Staulanza Hut you follow path n. 472, leave the Pelmo on the right to Città di Fiume Hut.
From there you follow "Alta Via delle Dolomiti n.1" and reach "Forcella Ambrizzola" (mt 2.277), then descend to the block of M.Mondeval till you see a great rock which has the tracks of some excavations done in the past.