The Loughcrew Cairns site is one of the four main passage tomb sites in Ireland, thought to date from about 3300 BC. The sites consist of cruciform chambers covered in most instances by a mound. A unique style of megalithic petroglyphs are seen there, including lozenge shapes, leaf shapes, as well as circles, some surrounded by radiating lines.

The site is spread across three hilltops, Carnbane East, Carnbane West, and Patrickstown. The Irish name for the site is Sliabh na Caillí, which means "mountain of the witch". Legend has it that the monuments were created when a giant witch, striding across the land, dropped her cargo of large stones from her apron. The orthostats and structural stones of the monuments tend to be made of local green gritstone, which was soft enough to carve, but also vulnerable to vandalism.

Situated just 3km east of Oldcastle in County Meath, the tombs are spread out over three different hills. Cairn T is one of the best preserved and most accessible tombs at Loughcrew and appears to be the central tomb of the whole complex. It faces the rising sun at the vernal (March) and autumnal (September) equinoxes which shines through the passage to illuminate symbols carved into the back wall of the chamber, corbelled roof and stunning examples of Neolithic art.

This tomb is reputed to be the resting place of Ollamh Fodhla a legendary King of Ireland. During the vernal and autumnal equinoxes, people traditionally gather at dawn to watch sunlight enter the Cairn T chamber and illuminate the interior of the tomb. A site of considerable historical importance in Ireland, Loughcrew Cairns is one of the jewels in the crown of the Boyne Valley.