The monument has been recognized as much more than a passage tomb. An ancient temple is a more fitting description of Newgrange because it is a place of astrological, religious and ceremonial importance.

In the 12th century, the mound and land around Newgrange become part of an outlying farm owned by the Cistercian Abbey of Mellifont. Because these farms were referred to as ‘granges’, by 1378 it was simply called ‘the new grange.

Newgrange is world famous for the phenomena around the time of the winter solstice in December when a single shaft of dawn sunlight penetrates and precisely illuminates the inner chamber.

Visitors to the historic site can experience the winter solstice illumination at any time of the year and this is often the highlight of the Brú na Boínne Visitor Experience official tour. Once every tour member is present inside, the lights are turned off, plunging the tomb into darkness. A light then simulates the sun as it would appear at dawn on the winter solstice, slowly illuminating the passageway and inner chamber. A lottery is held annually for tickets to allow just 20 people entry per morning to the tomb to view the actual event.

The east-west orientation of the passages at Knowth suggests an astronomical alignment with the equinoxes occurring in March and September. The alignment at Knowth does not however occur today due to the original entrances to the passages being destroyed, making it difficult to establish if an alignment existed in the first place.

Similar to Newgrange, the imposing mound at Knowth dates from around 3200BC and contains over a third of the total number of examples of Megalithic art in all of Western Europe including the oldest known illustration of the moon. Much of the artwork is found on the kerbstones, particularly those on approach to the passage entrances. Interestingly, some of this artwork was carved on the backs of the stones, known as hidden art.

A new visitor experience has recently opened at Knowth and includes improved interpretation to tell the story of the 50-year archaeological excavation of the site, its Megalithic art and its importance both nationally and worldwide.

There are two passages with chambers within the mound; the longest is the north passage at 59 ft leading to a cruciform chamber with an annex room off the right hand arm of the cross.

Like Newgrange, Dowth is aligned with the winter solstice. During this period in December, the setting sunlight penetrates the passage tomb and illuminates three stones within the central chamber.

Unfortunately, in 1847, the mound was subjected to a brutal excavation whereby two passage tombs were discovered but the mound was severely damaged in the process.

Whilst there is no access to the interior of the passage tomb, visitors can walk around the perimeter and take in the stunning views.

The entrance to Fourknocks is secured by a modern door, the key for which can be obtained from a house in the locality. It is a once in a lifetime experience to open an ancient passage tomb and step inside to explore with no one else around.

The 17 ft passage leads into a large, circular chamber with three recesses, giving it a circular cruciform shape. The interior is decorated with Megalithic art and includes what is possibly  the first depiction of a human face found in prehistoric art in Ireland. You can decide if it is indeed a smiling face or simply abstract art.

Fragments of 65 burials were found in the tomb, both the cremated and unburnt remains of adults and children. Decorated pottery, vessels and personal ornaments including pendants and beads were also found. All of the items were moved to the National Museum in Dublin.

Whilst Fourknocks is too far north to have a solar alignment, it is however aligned with the path of the winter solstice sunrise towards Newgrange. During stone age times, the passage tomb was aligned with the helical rising of the ‘W’ shaped constellation of Cassiopeia, perhaps accounting for the dominance of ‘W’ shaped zig zag engravings.