On the summit of Knocknarea is a large cairn about 55 metres (180 ft) wide and 10 metres (33 ft) high, making it the largest such cairn in Ireland outside the Brú na Bóinne complex in Meath. Although it remains unexcavated, and is one of the biggest of such monuments still unexplored, it has many of the features of a classic passage tomb. It is known in Irish as Meascán Méabha or Miosgan Meadhbha meaning Medb’s Lump (Miosgán means a lump or pat, especially of butter). In English it is known variously as Medb’s Cairn, Medb’s Tomb, Medb’s Nipple or Medb’s Grave (sometimes the name Medb is anglicised as Maeve). It is believed to date to around 3000 BCE.

Meabh is a figure in Irish mythology who features in stories dating to the early first millennium CE. As the story goes, the fiery Irish queen Medb was felled by a piece of cheese flung from an expert’s sling. After her death she was rumoured to have been buried atop Knocknarea. While the story of Medb’s burial is strictly legend, the massive cairn on top of the hill is very real. Archaeologist Stefan Bergh, in his book Landscape of the Monuments (Stockholm 1995), suggests that a large depression some distance to the west of the mound was the quarry from which the limestone for the monument was taken.