A little west of a Neolithic court tomb on Slievemore Mountain, Achill - the largest island off the northwest coast of County Mayo, Ireland, around 100 kilometres northwest of Galway - are two adjacent sites, described in the 1890s as a 'sepulchral complex'.
     Some archaeologists regard the eastern part as a collapsed megalithic tomb, and either a secondary burial mound or a later construction, while others see either a series of collapsed early medieval huts or a post-medieval agricultural building.
     In the summer of 2014, a two year project began to survey and partially excavate the sites as part of ongoing investigations into the archaeology of Slievemore, and focused on the western 'tumulus'.
     What appeared to be a small circular mound turned out to be one side of a large enclosure - at least 15 by 20 metres - defined by two concentric bands of in-filled stone walling. A southern entrance is marked by two prominent standing stones, later employed as the entrance to an oval building containing a series of overlying hearths. This building was replaced by a smaller circular building defined by a simple turf bank, which gave the appearance of a circular mound with a central hollow.
     A series of closely spaced pits and post holes seem to be part of the primary period of activity within the enclosure. The pattern of postholes does not suggest a structure, but their depth and diameter indicates that substantial timbers were used. The pits were among the most interesting features. One was a rectangular, and lined with stone slabs. An adjacent pit was almost perfectly circular, with vertical sides and a flat base, the bottom covered by a single flat stone slab which fitted precisely. At the eastern edge of the excavation, a much larger pit several metres across was partially investigated, and found to be filled with an assortment of large stones.
     Work in 2015 will concentrate on completing investigation of the interior of the enclosure, and examining the various stone structures that make up the 'cromlech'.
     The enclosure is already a very exciting discovery, possibly associated with a large number of prehistoric enclosures elsewhere in County Mayo, such as those at Ceide [KAY-ja] Fields - the famous Neolithic field systems along the north Mayo coast.

Edited from Past Horizons (9 April 2015)