Carrowmore (Irish An Cheathrú Mhór "the great quarter") in County Sligo is the most concentrated (mostly arranged in rows) accumulation, dated between 4000 and 2500 BCE. Most of the 25 better-preserved systems, from once over 80 (some say over 200), are located on an area of more than three square kilometres near the access road.
They mainly consist of small passage tombs and dolmens. Few of them still have the circle of curbs, as they were probably originally under a cairn. The complexes are older than Newgrange and belong to the beginning of the Irish megalithic (circa 3850 BCE). The largest complex in the area (No. 51) is Listoghil, a passage tomb with rock carvings, excavated under a cairn. Plant No. 7 - according to the numbering by G. Petries from 1837 - has a certain resemblance to the Danish Runddysse Poskær Stenhus on Djursland. In some ways, the Carrowmore complexes are atypical passage graves. For example, none of the passage tombs has a tunnel-like passage which is a feature of most Irish passage graves, and only Tomb 51, (Listoghil) has a cairn.