You can wander around the church and friary/college on top of the Hill of Slane all morning without noticing the mound known as “the motte” because it’s in a wooded area behind the church. I know I (who grew up in Co. Meath) didn’t even know it was there until I read about it somewhere or other. There now seems to be a very interesting project to investigate this mound under way. Archaeologists have been scanning the motte and its surroundings (an earth resistance survey) to discover what it’s made of (a cairn of rocks brought from elsewhere, a built structure, or a mound of local clay?) and detect any subsoil evidence of the remains of buildings on top. The resultant 3D mapping gives a great view of the physical features of the hill and suggests future locations to explore.
Going by the annals, it seems likely that there was an ancient grave of some importance on the hill: reputed to be the Fir Bolg king Sláine, from whom the hill gets its name. (Yes, that’s the same Sláine on whose legends the classic 2000AD comic was inspired. I daresay a generation of British and Irish megalithomaniacs had their imaginations kick-started by that story.) The type of grave this may have been (cairn, passage tomb, dolmen, etc.) we don’t know. Likewise, whether that grave site was later exploited to build a Norman motte and bailey-type fortified position or whether the church was originally built on the tomb site is unknown. It seems the use of the motte as a fortified position dates from around 1170AD, but the mound now known as the motte could be much older. Sláine was reputed to have cleared the site for Newgrange, which would place him circa 3200BC. However, the preliminary earth resistance survey results from this project are intriguing, suggesting that the mound is man-made and revealing a second earthwork (possibly a ring barrow dating from 2500BC–although all dates seem approximate at this stage in the project) partially overbuilt by a rath surrounding the motte. Given the history of adaptive re-use of sites with strategic or symbolic significance by successive cultures in Ireland, there certainly seems to be a strong case for further investigation.
Fieldwork has been ongoing since 2010, so this is a project to bookmark and watch for future discoveries.