To the east of Slane, between a U-bend in the River Boyne and the N51 to the north, Brú na Bóinne encompasses the spectacular 5000-year-old passage graves of Newgrange, Knowth and Dowth, high round tumuli raised over stone passages and burial chambers. Entry is funnelled through the impressive visitor centre on the south side of the river, which provides detailed information on the significance of the sites, their construction and artwork, and the Neolithic society that created them, as well as housing a tourist information desk and café. A footbridge crosses from the centre to the north side of the river, where the compulsory minibuses shuttle you to Newgrange and Knowth, which have both been comprehensively excavated and reconstructed, for guided tours. The passage tomb at Dowth, which has been badly damaged by road-builders and cack-handed nineteenth-century archeologists, is closed to visitors.

Newgrange

Newgrange is unquestionably the most striking of the Brú na Bóinne mounds, not least because its facade of white quartz stones and round granite boulders has been reassembled. The quartz originally came from Wicklow, the granite from the Mourne and Carlingford areas, exemplifying the mind-boggling levels of resources and organization lavished on this project, by these farmers who used nothing but simple tools of wood and stone. It has been estimated that the tumulus, which is over 75m in diameter, weighs 200,000 tonnes in total and would have taken around forty years to build. It was the final resting place of a high-status family within the Neolithic community – the cremated remains and grave goods of at least five people were recovered from the burial chamber during excavation – but seems also to have had a wider purpose as a ritual site or gathering place.

The entrance stone is one of the finest examples of the art of the tomb-builders, who carved spectacular but enigmatic spirals, chevrons, lozenges and other geometric designs onto many of the large stones around the mound and up the nineteen-metre passage. The tomb’s pivotal feature, however, is a roof-box above the entrance whose slit was perfectly positioned to receive the first rays of the rising sun on the day of the winter solstice (December 21); the light first peeps into the cruciform burial chamber itself before spreading its rays along the length of the passage. The engaging guided tour provides an electrically powered simulation in the burial chamber, while tickets for the real thing are decided by lottery each year. To prehistoric farmers, this solstice marked the start of a new year, promising rebirth for their crops and perhaps new life for the spirits of the dead.

It seems probable that by around 2000 BC, in the Late Neolithic or Early Bronze Age, the mound had collapsed and fallen into disuse, but it still provided a powerful focal point for ritual. During this era, a huge religious enclosure known as the pit circle was constructed here, consisting of a double circle of wooden posts, within which animals were cremated and buried in pits. To this was added a circle of around 35 standing stones, which may have had an astronomical function; about a dozen of them remain upright.

Knowth

It’s well worth signing up for the lively guided tour of Knowth too, which provides some telling contrasts with the more famous Newgrange – not least in interpretation: the archeologist in charge of this site, for example, thought the white quartz stones discovered around the main passage entrance were to reflect the sun, so left them as a shimmering carpet on the ground. The Knowth mound is pierced by two passages, each around twice the length of the Newgrange tunnel, aligned roughly with sunrise and sunset on the equinox days in March and September and leading to back-to-back burial chambers. Unfortunately, it’s no longer possible to follow the passages themselves, but the tour takes you inside the mound to look along the eastern tunnel, and you can also climb on top of the mound for views of the Hill of Slane and the Wicklow Mountains.

Knowth is even richer in Neolithic art than Newgrange, with about 250 decorated stones discovered here – over half of all known Irish passage-tomb art. The mound is surrounded by over 120 huge kerbstones, one of which supports a carved pattern of crescents and lines that may represent the equinox; elsewhere, patterns of circular and serpentine incisions have been interpreted as local maps, showing the River Boyne and the burial mounds. Hard by the main mound, you can poke around eighteen smaller or satellite mounds, at least two of which were built before the main tomb. The Knowth mound attracted habitation in various eras right up until the sixteenth century AD, and your guide will show you several souterrains, underground tunnels that were dug in the early Christian period for hiding, escape and possibly food preservation.