It is over 4 metres (13 ft) high and 100 metres (330 ft) in circumference. It consists of a circle of 30 concrete columns topped by a ring of stone.
Achill-henge was constructed over a weekend in November 2011 by the property developer and protester Joe McNamara. A team of workers hauled the large concrete slabs up the hill and sank them in the bog.
Mayo County Council requested a court order to force McNamara to remove the edifice as it had been built without planning permission. McNamara claimed that the structure was exempt from planning rules as an "ornamental garden".
Theresa McDonald, Director of the Achill Archaeological Field School, had also raised objections on the grounds that the structure may be less than 500m from a Bronze Age archaeological site.
The High Court required McNamara to cease further work on the site, and as he was found to be in breach of this, he was jailed for three days for contempt of court. The Court referred the planning decision to An Bord Pleanala, which in July 2012 upheld the Council's decision.
Some local people have expressed admiration for the work as a feat of engineering, and a newspaper poll found a majority of locals in support of keeping the structure.
Joe McNamara is noted in Ireland for a series of protests against Anglo-Irish Bank and the government's handling of the Irish financial crisis. In particular, he drove a cement mixer through the gates of the Irish parliament building Leinster House.
McNamara described Achill-henge as "a place of reflection".
- Kieran Cooke (16 February 2012). "Achill-henge: A monument that divides Ireland". BBC News. Retrieved 3 September 2012.
- Cathy Hayes (13 January 2012). "Archaeologist objects - Achill-Henge may be built over prehistoric site - VIDEO". Irish Central. Retrieved 3 September 2012.
- Caroline Crawford (24 July 2012). "Video: Developer Joe McNamara’s ‘Achill-henge’ project refused by Bord Pleanala". Irish Independent. Retrieved 2 September 2012.
- "Prime Time - 8th January 2013". RTE News. 9 January 2013. Retrieved 9 January 2013.
- Edwin McGreal. "Anglo Avenger ordered to take down Achill-henge". The Mayo News. Retrieved 3 September 2012.