Brú na Bóinne Visitor Centre interprets the Neolithic monuments of Newgrange, Knowth and Dowth. The extensive exhibition includes a full scale replica of the chamber at Newgrange as well as a full model of one of the smaller tombs at Knowth.
The iconic passage grave is really worth a visit.
Donore, Co. Meath, A92 EH5C
http://www.worldheritageireland.ie/bru-na-boinne/
https://www.newgrange.com/index.htm