Mt. Ida is easily reached as a sidetrip to the Cass saddle/Lagoon saddle track near Arthur's pass. Just follow the 4WD track along the Harper valley and you will soon see it. On the true left side of the Harper river you can see another 4WD track going up a river terrace. Just follow it and you will finally come to enjoy this view. You can either walk back to Hamilton hut or West Harper hut, completing the 3day Cass saddle walkor you can follow the 4WD track to a gravel road and hope for a ride out if you haven't arranged for transport. The 4WD track is on private land, so it may be advisable to ask for permission first.
The huge gap is on the NE face and can be easily identified on the map. The same with the debris cone. The pic was taken from the little hill (974m) about 4km NE of the summit of Mt. Ida. The lake on the left is Lake Catherine, to the right is the Harper river and a hill called Gargarus (1665m).