Cache on the "RED" loop, a circular 5km route with a (very) steep 250m ascent up the "Cardiac Steps".
The views from the area around the cache are superb on a nice day. The cache location itself will bring you to a beehive hut, which has a well in front of it. Cache is not hidden in or on the hut. It was built back in the seventies when the trail was opened. Think burly workmen grabbing a cuppa out of the rain, rather than ascetic monks contemplating solitude 
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In all cases do not walk on the main road. It is dangerous, and not required as there is a walking path running parallel inside it. At the upper part of the trail there are paths criss-crossing in places so a little navigation should be expected.
There are three suggested starting points.
1. Torc Parking. Leaving Killarney, this is a small bit past the main parking for the waterfall, and on the right. Also a quieter spot for parking! There is a rough path on left hand side inside the main road. Do not walk along the road for safety sake - it is not suitable for pedestrians. This flat 1km walk will give you a recommended "warm up" prior to the steps.
2. Dinis Cottage. Park here, hop out of the car and go straight for it! Cross the road and after a very short walk you are at the start of the steps.
3. Upper Torc Carpark. A slightly less strenuous option - cross the bridge over the waterfall and manoeuvre along to GZ. Return back the same way.