The importance of Sligo's location in prehistory is demonstrated by the abundance of ancient sites close by and even within the town. For example, Sligo town's first roundabout was constructed around a megalithic passage tomb at Abbeyquarter North in Garavogue Villas. This is an outlier of the large group of monuments at Carrowmore on the Cuil Irra peninsula on the western outskirts of the town. The area around Sligo town has one of the highest densities of prehistoric archaeological sites in Ireland, and is the only place in which all classes of Irish megalithic monuments are to be found together. Knocknarea mountain, capped by the great cairn of Miosgan Maeve, dominates the skyline to the west of the town. Cairns Hill on the southern edge of the town also has two very large stone cairns.