Magh Slecht packs more than 80 ancient monuments into about three square miles – one of the densest ritual landscapes in Ireland – and it is also the plain that gave its name to the 1256 battle that tore the kingdom of Breifne permanently in two. It lies in the south-east of Templeport parish in west County Cavan, classic drumlin country bounded by Templeport Lough to the south, Slieve Rushen to the north, the Shannon–Erne Waterway to the east and the River Blackwater to the west.
A warning worth giving up front: this is a place you read about more easily than you visit. Almost nothing is signposted, and most of the monuments sit in private fields well out of view from the road. Come for the history and the lore; do not come expecting a heritage trail.
The 1256 battle
By the mid-13th century the kingdom of Breifne was split by a power struggle between the O’Rourke lords and their O’Reilly vassals, each pulling in outside allies – the O’Connor kings of Connacht on one side, Walter de Burgh and the Anglo-Normans on the other. The two armies were meant to meet at Lough Allen, but the O’Reillys came under heavy attack in the townland of Seltanahunshin, in County Leitrim, and fell back northwards. Aedh O’Connor’s cavalry ran them down at the townlands of Bellavally Upper and Legnaderk, and the battle was fought there.
It was a decisive O’Rourke–O’Connor victory. The O’Reillys lost their king, Cathal Ua Raghallaigh, and their commander Cúchonnacht Ua Raghallaigh. Yet winning the field did not put the kingdom back together: Breifne was left permanently divided into West Breifne under the O’Rourkes (roughly modern Leitrim) and East Breifne under the O’Reillys (roughly modern Cavan), a line that shaped the county for centuries. The battle is recorded in the Annals of Connacht and the Annals of the Four Masters.
Crom Cruach and the older plain
Long before the battle, this was sacred ground. The plain was first called Magh Senaig, the ‘plain of the hill-slope’, and appears under that name in the Metrical Dindshenchas. It became Magh Slécht – read either as the ‘plain of prostrations’, for the worshippers who knelt here, or as a ‘grave-strewn plain’ for all its tombs – when it grew into the cult centre of Crom Cruach, said to have been the chief pagan idol in Ireland, standing at Killycluggin and Kilnavert. The most vividly recorded act of Saint Patrick’s mission is his casting down of that idol with his crozier, the Bachal Isu.
The archaeology backs up the reputation. Across the three square miles are nine megalithic tombs, seven ring barrows, three stone circles, nine standing stones, two stone rows, several enclosures and crannogs, more than thirty ráths and souterrains, early church sites, holy wells and two medieval castles. One practical catch for visitors: the Killycluggin stone you can see by the roadside is a replica – the original, carved in La Tène style and linked to the Crom Cruach cult, is in Cavan County Museum at Ballyjamesduff.
Visiting
There is no visitor centre, car park or marked trail. The usual approach is to park at the Bellavally lay-by off the R200, where roadside space is limited, and explore from there on foot. Go in summer (May to September) for firmer ground and long light, wear boots, and bring an OS map or an offline GPS track, because the monuments are scattered, mostly on private farmland, and mobile signal drops in the hollows between the drumlins. Stick to field boundaries and public roads and respect any ‘no entry’ signs – this is working land.
If you want to actually see the carved stone the place is famous for, the surest plan is to pair a drive across the plain with the half-hour run to Cavan County Museum at Ballyjamesduff, which holds the genuine Killycluggin stone and tells the wider story of the O’Rourkes, O’Reillys and Normans.