Garn Boduan is a titanic hill-top enclosure, about 512m from north to south by 384m, defined by two successive and somewhat divergent stone-walled rampart circuits. Within are about 170 circular stone walled structures, generally in the region of 5.2-7.3m in diameter. Upon the highest, eastern edge, of the site is a small stone-ramparted enclosure, about 70m from north to south by 30m. Both the greater and smaller enclosures have two gates, one of each being anciently blocked. A single sherd of pottery indicates second century AD occupation.

During a field visit on 16 April 2005 by the Hillfort Study Group some damage to the inner 'citadel' was noted from the recent construction of stone built shelters on the summit.

Sources: Hogg 1962 (Arch. J. 117 1960), 1-39;
RCAHMW 1964 Caernarvon III, 22-4.

RCAHMW, August 2011.