Somewhere beneath the surface of a Kildare bog, a road runs for roughly 1,400 metres through peat that has been quietly preserving it for centuries. You would not know it was there without looking carefully; the only sign above ground is a line of unusually lush heath growth running north-east to south-west, the vegetation feeding on the gravel and marl beneath and betraying the road's course to anyone who knows what to look for. Locally, the track was called 'The Dane's Road', a name of the kind often attached in Ireland to ancient infrastructure whose true origins had been forgotten.

The road is a togher, a term for a causeway or trackway built across boggy ground, typically constructed of timber, stone, or compacted material to allow passage over otherwise impassable terrain. This particular example was one of three toghers converging on Derrybrennan townland, a small island of elevated ground rising out of the broad expanse of bog north of Lullymore. It connected that higher ground with Ballybrack townland to the north, and came to the attention of researchers after Bord na Móna, the state peat-harvesting company, reported its discovery. Excavation followed in 1964 to 1965, carried out by Rynne on behalf of the National Museum of Ireland. The portion examined was built from gravel and marl laid to a width of three metres and a thickness of between 0.2 and 0.25 metres, sitting about half a metre below the shrunken but uncut bog surface. The convergence of three such routes on a single small island of dry land suggests that Derrybrennan was once a place of some significance, a crossing point or gathering place in a landscape that would otherwise have been deeply difficult to traverse.