There are a lot more archaeological sites in the Republic of Ireland than we thought

Ringfort at Cam, Co. Roscommon


How many archaeological sites are there in the Republic of Ireland? This is an obvious question but not an easy one to answer. If we consult the statutory Record of Monuments and Places (RMP) established under the National Monuments Act (1930-2004) the answer is about 140,000 ( But we now know that the RMP only lists a fraction of the potential surviving sites. During the Celtic Tiger period (1995-2008) thousands of previously unknown sites were identified during the course of development. This is because archaeological remains may be buried beneath the ground or later structures and are not visible to the naked eye. Archaeological remains that are standing above ground may be obscured by overgrowth, may be covered by later structures or may have been partly removed or altered to make them unrecognisable. Archaeological remains that are standing above ground may be in plain view but may not have been recognized or mapped or noted in surveys or reports.

So how many sites are there? A quantitative approach would appear to be the most useful approach to answering the question. The land area of Ireland is 6,888,900 hectares (ha), dividing this by the roughly 140,000 sites included in the RMP results in a ratio of one site per 49 ha. Using this as a starting point the general number of potential sites can be estimated by using information now becoming available from the recent large-scale archaeological investigations of infrastructure projects like motorways and pipelines. All the large-scale infrastructure projects developed during the Celtic Tiger period have resulted in the discovery of large numbers of archaeological sites. For example the Bord Gáis “Pipeline to the west” construction corridor was 335 km long and impacted an area of 1,005 ha. During the course of the development 190 previously unknown archaeological sites were identified, one site per 5.3 ha (See Grogan et al. 2007, 5- 9). Similarly, during the construction of the Cork to Dublin gas pipeline 96 monuments were impacted over a distance of 222 km, an area of 489 ha, one site per 5 .1 ha (See McQuade et al. 2000, xiii). During the construction of the M8 Motorway from Ballycuddahy, Co. Laois to Dunkettle, Co. Cork 249 sites were indentified in an area of 1,494 ha, or one site per 5.6 ha (Also McQuade et al. xiii).

Using these figures we can calculate an average ratio of sites to hectares of one site per 5.6 ha. Scaling this up to the total land area of the Republic  suggests that as many as 1.23 million sites potentially remain to be identified. Of course the infrastructure projects tended to be situated in the fertile lowland areas, where sites cluster, and sites may be potentially less likely to be found in upland areas, so this figure should be adjusted a little. However, these comparisons suggest that the RMP represents somewhere around 11% of the total potential sites. These quantitative figures suggest on the one hand that almost any development has the potential to impact archaeology with those impacting 5.6 ha or more approaching an almost certainty. The risk of impacting archaeology cannot be ruled out without the deployment of field-based assessment methods such as archaeological testing or geophysical investigation. On the other hand acknowledging that there are probably more than a millions potential sites should cause archaeologists to question some of their assumptions about managing the resource.


Grogan et al. 2007. The Bronze Age landscapes of the pipeline to the west. Dublin, Wordwell.

McQuade et al. 2009. In the shadow of the Galtees: archaeological excavations along the N8 Cashel to Mitchelstown Road Scheme. Dublin. NRA Scheme Monographs 4.

Mount, C. There are a lot more archaeological sites in the Republic of Ireland than we thought. The Charles Mount Blog, May 18, 2011.