Brú na Bóinne - Archaeological Ensemble of the Bend of the Boyne

The three main prehistoric sites of the Brú na Bóinne Complex, Newgrange, Knowth and Dowth, are situated on the north bank of the River Boyne 50 km north of Dublin. This is Europe's largest and most important concentration of prehistoric megalithic art. The monuments there had social, economic, religious and funerary functions.

http://whc.unesco.org/en/list/659

Brú na Bóinne - Archaeological Ensemble of the Bend of the Boyne consists of 3 large and 37 small burial mounds or passage tombs from the Neolithicum. The complex dates from 3300 - 2900 BCE. It has been made a WHS because of its artistic value and its size (the biggest remains from the Neolithic era in Europe).

The three most well-known sites within this complex (called Brú na Bóinne in Irish) are the impressive passage graves of Newgrange, Knowth and Dowth. 

http://www.worldheritagesite.org/sites/bendoftheboyne.html

Sceilg Mhichíl

This monastic complex, perched since about the 7th century on the steep sides of the rocky island of Skellig Michael, some 12 km off the coast of south-west Ireland, illustrates the very spartan existence of the first Irish Christians. Since the extreme remoteness of Skellig Michael has until recently discouraged visitors, the site is exceptionally well preserved.

http://whc.unesco.org/en/list/757

Sceilg Mhichíl (Skellig Michael) is an early monastic complex on a difficult to access, steep rocky island. The island, also known as Great Skellig, lies about 15 kilometres west of the coast of County Kerry, Ireland. It is the larger of the two Skellig Islands.

For 600 years the island was an important centre of monastic life for Irish Christian monks. An Irish Celtic monastery, which is situated almost at the summit of the 230-metre-high rock, was built in 588. The very spartan conditions inside the monastery illustrate the ascetic lifestyle practiced by early Irish Christians. The monks lived in stone 'beehive' huts (clochans), perched above nearly vertical cliff walls.

The buildings on the island consist of the Monastery (including an oratory and St. Michael's Church) and the Hermitage.

http://www.worldheritagesite.org/sites/skelligmichael.html