4 sits within that extraordinary cluster as a quietly compelling example of Neolithic monument-building at its most elemental. A passage tomb is exactly what the name suggests: a stone-lined corridor leading into a central burial chamber, the whole structure typically covered by a cairn of earth or rubble. What makes Carrowmore as a group so unusual is the sheer density of monuments arranged across a low-lying drumlin landscape, within sight of one another and of the great cairn on Knocknarea to the west.

The tomb carries the designation Petrie no. 4, a numbering system that traces back to the antiquarian work of George Petrie, who surveyed and catalogued monuments at Carrowmore in the nineteenth century before later scholars refined the record. The fullest modern treatment of this particular tomb appears in Seán Ó Nualláin's survey of the megalithic tombs of County Sligo, published in 1989 as the fifth volume of a national inventory. Ó Nualláin's work brought systematic documentation to a complex of monuments that had suffered considerably from land clearance, stone robbing, and earlier excavation of variable quality. The central chamber, visible from multiple angles in the photographic record, is the structural heart of the monument, the space where cremated remains and grave goods would originally have been deposited. It is now a protected National Monument in State care.