Approach
From the small parking after the tunnel, take the path that starts at the right side of the embankment wall. Follow the red-and-white signs switchbacking uphill and atop the prominent overhanging cliff (ca. 15 min). Continue along contour and look for small turnoffs left leading to sectors B (some scrambling), C and later D along the path.
OSM-Map will help: http://www.openstreetmap.org/#map=17/45.86445/10.82647