Due to the rocky nature of the Cuillin they have historically been of little use for agriculture: this contrasts with the majority of the highlands, where the hills were used to provide seasonal grazing for cattle and sheep. Despite the lack of earlier human presence in the hills themselves, there is much evidence of historic settlement in the surrounding glens, with prehistoric hut circles found in Glenbrittle, and a stone circle identified in Glen Sligachan. Rubha an Dùnain, an uninhabited peninsula to the south of the main ridge, has a variety of archaeological sites dating from the Neolithic onwards. There is a 2nd or 3rd millennium BC chambered cairn, an Iron Age promontory fort and the remains of another prehistoric settlement dating from the Bronze Age nearby. Loch na h-Airde on the peninsula is linked to the sea by an artificial "Viking" canal that may date from the later period of Norse settlement.