Medieval Irish texts say that five great roads, each called a slighe, ran out from Tara to the corners of Ireland. The texts are clear about the names and much less clear about the routes. Nothing on the ground has been shown to be one of these roads along its length, and the routes drawn on modern maps are reconstructions.
Route as the sources give it Reconstructed
To Slane, through the Moyry Pass north of Dundalk, round Slieve Fuaid near Newtownhamilton, to Emain Macha, ending at Dunseverick on the north Antrim coast.
On the ground
Dunseverick, where traces of an Iron Age promontory fort were found, has long been taken as its northern end. No length of the road itself is described as excavated.
Wikipedia: History of roads in Ireland (Five great roads) ↗ · Wikipedia: Dunseverick Castle ↗ · Emain Macha
Route as the sources give it Reconstructed
Through Dublin, crossing the Liffey by a hurdle bridge, into the old district of Cualu and on south, towards Waterford.
On the ground
The line is argued over. George Petrie in 1839 sent it inland through Ratoath to Dublin; Henry Morris in 1938 rejected that and traced it through Swords, then west of the Wicklow Mountains by Baltinglass and Leighlinbridge and down the Barrow towards Waterford, from later Norman references to Bóthar Chualann. The Wicklow Way’s Irish name, Slí Chualann Nua, borrows the name; it is a 1980 walking trail.
Route as the sources give it Reconstructed
Due west towards Lough Owel in Westmeath, then to Cruachan (Rathcroghan).
On the ground
The Uisneach article says it linked Tara and Uisneach and that the modern R392 mostly follows it. That is a different line from the Lough Owel route the roads article gives, and neither article says how the route was fixed.
Wikipedia: History of roads in Ireland (Five great roads) ↗ · Wikipedia: Hill of Uisneach ↗ · Rathcroghan · Uisneach
Route as the sources give it Reconstructed
Towards and through Ossory in County Kilkenny.
On the ground
The articles give no more than the direction. We found no source that traces it on the ground.
Route as the sources give it Reconstructed
Joined the Esker Riada near Clonard and followed it, more or less, to County Galway. The Four Masters call it the Eiscir Riada, the line that split Ireland between Conn’s Half and Mugh’s Half.
On the ground
This is the one road with a real landscape behind it. The Esker Riada is a chain of glacial gravel ridges, left about 10,000 years ago, that gives dry footing through the midland bogs. It links Clonard, Durrow and Clonmacnoise, and the N6 Dublin to Galway road still roughly follows it. The ridges are real; the exact line of a road along them is not recorded.
Wikipedia: History of roads in Ireland (Five great roads) ↗ · Wikipedia: Esker Riada ↗ · Bogs
None of these is one of the five roads. They are what excavation has actually found: plank and brushwood tracks across bogs, preserved because the bog swallowed them. More on the bogs page.
Slighe Midluachra to the north, Slighe Cualann to the south-east, Slighe Assail to the west, Slighe Dala to the south-west and Slighe Mhór along the Esker Riada to Galway. The names come from medieval texts; the routes are later reconstructions.
Probably not. The Wikipedia articles on Slíghe Chualann and on the history of Irish roads both say the routes more likely met at Dublin, at the ford of hurdles over the Liffey.
No. Ireland was never part of the Roman Empire. It did have plank and brushwood trackways across bogs, such as the Corlea Trackway of 148 to 147 BC, and at least one stone-surfaced Iron Age road in Munster.
A highway. The early medieval law tracts use slige for the widest class of road, one on which two chariots could pass.
Gaps: Wikipedia has articles for only one of the five roads, Slíghe Chualann; the others are described in the Hill of Tara and History of roads articles. We have not read the Irish texts themselves, and we have not drawn the routes on a map, because no source fixes them closely enough. Slighe Dala in particular is known only by its direction.
Know a study that traces one of these roads? Tell us.