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.

The outside is impressive enough, with its re-constructed stone facade, but it is the opportunity to go inside the mound that makes this one of the can't miss sights of Ireland. Imagine a dry stone construction so exact that it has remained watertight for over 5,000 years, and still admits sunlight only on the morning of the winter solstice. If you can, go first thing in the morning so that your tour will not be too crowded. Also, while you are there, take the tour to Knowth as well. While not as awe-inspiring (largely because of the lack of interior access) there are several things you can see at Knowth that you cannot see at Newgrange. However, if you have time for only one of the two, it must be Newgrange.