I walked around the edge of the triangular field where this monument is supposed to be and couldn't see a thing, so I went to a nearby house to ask about it and the owner told me that it was where I thought it was and also told me a lot of local stories. One of them was about the cliff stack that can be so clearly seen from this area. The stack only broke away from the mainland in the mid 19th Century, until when it was an arch. That must have looked spectacular. Many years ago, when fishing around the stack, a hare could be seen living on the stack, probably dropped by a bird of prey and at one time there was the remains of a building, a doorway, to be seen on there, too. The best thing he told me about was Polladarky, however, but more of that shortly.
The reason I couldn't see this monument from the road is that the remains only protrude about 15cm from the ground. The tops of the orthostats forming the gallery can be just made out if you are standing very close to them. The area that can be traced is about 1.5m wide and 4m long.
A short walk down the track to the east of the tomb takes you to Polladarky. On the map this looks like a small lough or something - just a blue splodge. In reality it is one of the most spectacular natural features I have seen in Ireland! There must have been a cave in the cliff here at some point, eaten out by the sea, with a narrow tunnel leading into it. Then the roof collapsed, leaving a 70m x 50m hole about 40m deep into which the sea rushes through a narrow tunnel in the cliff face. To stand on the edge of this in calm weather is quite unnerving. In rough seas the sight below must be turmoil, but I personally wouldn't like to stand too close to the edge to see it.
This is an explanation of (and a bit of a disclaimer for) the coordinates I provide.
Where a GPS figure is given this is the master for all other coordinates. According to my Garmin these are quite accurate.
Where there is no GPS figure the 6 figure grid reference is master for the others. This may not be very accurate as it could have come from the OS maps and could have been read by eye. Consequently, all other cordinates are going to have inaccuracies.
The calculation of Longitude and Latitude uses an algorithm that is not 100% accurate. The long/lat figures are used as a basis for calculating the UTM & ITM coordinates. Consequently, UTM & ITM coordinates are slightly out.
UTM is a global coordinate system - Universal Transverse Mercator - that is at the core of the GPS system.
ITM is the new coordinate system - Irish Transverse Mercator - that is more accurate and more GPS friendly than the Irish Grid Reference system. This will be used on the next generation of Irish OS maps.