Loughcrew Cairns
     

The Loughcrew cairns are a Stone Age cemetery (c. 3200 BC) comprising some 30 passage tombs, situated on three hill summits outside Oldcastle. The hills, known collectively as "Sliabh na Caillighe", or the "Mountain of the Witch" and sometimes "The Storied Hills", are individually called Carnbane West, Carnbane East (the highest point in Meath) and Patrickstown. The cairns may be older than Newgrange (some 40km to the South East) but were only discovered in the Nineteenth Century by a School Inspector named Eugene Conwell who gave the cairns their letter names.

One of the best-preserved cairns can still be accessed, Cairn T, the reputed tomb of the druid, Ollamh Fodhla. Fodhla instituted the Tara triennial feis and conducted ceremonies on Loughcrew to acquire laws from the spirit world, which were taken to Tara to be distributed throughout the land by the High King.

Cairn T faces the rising sun at the spring and Autumnal Equinoxes which shines through the passage to illuminate sun symbols at the back of the chamber. The beam of sunlight is shaped by the upright and the sill stones in the passageway so that a bright rectangle moves diagonally across the stone as the sun rises, illuminating each of a series of sun symbols in turn. 

According to Frank Prendergast of the Dublin Institute of Technology it suggests that settlers in the area were familiar with the yearly cycle of the Sun and perhaps centred their lives around it.
Image courtesy of http://www.knowth.com/loughcrew.htm

Cairn T is known locally as "the witch's cave" after Garavogue who is said to have dropped the big heaps of stones from her apron as she hopped across the hill. On the Cairns north-side is a stone seat known as the Hag's Chair, where Garavogue sat and watched the stars. A cross carved on the seat dates from Penal times when open-air masses were held here.
 
Cairn U, north east of Cairn T, has a stone bisected by a shadow at Summer Solstice, and its passage is aligned to 4 February and 8 November cross-quarter days, like the passage tomb at Tara. Cairn V, south east of Cairn T, marks the winter solstice. Y-shaped Cairn S, north west of Cairn T, marks sunsets on 6 May and 8 August cross-quarter days. A stone at Cairn N, south west of Cairn T, aligns on the Hill of Fore to mark the winter solstice sunset.