Go to the village of Dromahair in Co Leitrim & take the Sligo road on the south side of Lough Gill. After a mile or two, there's a lane leading down to a place you can look over to the island which is the object of Yeats' poem-the island is heavily wooded, so not much heather now, if any! You can find the hill where the 'Fiddler of Dooney' played, another Yeats poem- it's on the same road.
It has nothing to do with Richard Farrelly's song, although I'm glad to know it IS an Irish song & not composed in the US for Bing Crosby, as I always thought- thanks for all this!!