I don't have too much to add to the previous post, except to reiterate 'wow!' We only had time for the Newgrange tour - wish we could've seen Knowth, too. Drove by Dowth and walked around a bit but it's pretty damaged by now, with no interior access.

Newgrange predates the pyramids in Egypt and Stonehenge, so be prepared for your imagination to soar. Terrific art on stone with many swirls and whirls. Very friendly and patient staff. Nice little gift shop at the visitor center, and the exhibitions there added to the experience. A must do if you're in the Dublin area.

Oh, and if you're driving, look for the signs that say 'Slane' and/or 'Bru na Boinne.' It won't say Newgrange. I drove around for an hour looking for it. Also, it really is a good idea to arrive around 9.30 am (opening time in October, anyway) and get on the first tour (10 am). It gets more and more crowded as the day progresses.