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1. Newgrange's two neighbours-Knowth and Dowth The latter means place of darkness and is aligned on the winter solstice sunset as opposed to Newgrange's sunrise. Knowth has equinoctal alignments

2.Big passage grave cemetery at Loughcrew, Cairn T isthe most famous.

3.Carrowkeel. passage grave cemetery on a mountaintop. Many have 'lightboxes' for the sun to enter

4.Carrowmore various types of chamber tombs and dolmens,some very early.

5.Fourknocks. Nice passage grave with an entrance stone carved with zigzags and very round chamber

6.Queen Maeve's cairn. Giant unopened passage grave

7.Mound of the Hostages on Tara.Mentioned in mythology.

There are many others, plus dolmens,wedge graves and court cairns, in various staes of repair all over Ireland

Did you try googling 'passage graves+Ireland'? You should get quite a few ....

this may be of some help to you, makes interesting reading anyway http://www.carrowkeel.com/files/main.html