The Irish countryside is liberally dotted with traces of the people who have inhabited the island over the past 9,000 years.

In some instances the "trace" may consist of a lost or discarded flint or bronze implement, in others a scatter of broken pottery. Either can constitute the first perceived evidence of the existence of a dwelling-site or grave. Some sites are instantly recognisable as ancient monuments, as in where a cluster of stone buildings, including a Round Tower are found grouped around a High Cross.

This immediately suggests the remains of an Early Christian monastery. Others, however, are not so easily recognised or interpreted. A collection of large stones in the corner of a field is not always immediately identified as the remains of a megalithic tomb of prehistoric times. Some sites have no surface indications at all, or at best only a few humps or bumps whose significance is only revealed by ploughing or other disturbance.

It is not necessarily the age of the site or monument which dictates its state of preservation. The materials from which it was originally made are much more influential. Structures made of organic materials, such as wood, decay quite rapidly and often leave little or no trace. Those made of earth can be eroded, literally washed away, in the course of time. Structures in stone can, of course, be thrown down and dilapidated but the stones themselves will endure, unless deliberately removed from the site.

Many of the monuments to be seen in the countryside, like many of the artefacts we see in museums, are incomplete. Often the more valuable elements have disappeared: the stone axe lacks its wooden haft, the earthen rampart its timber palisade, the stone castle its wooden floors, the Georgian house its roof.

Throughout Irish history and prehistory structural materials have dictated the preservation of sites, monuments and artefacts. More recently, however, human interference in the form of "development", along with simple neglect and acts of war, has in many cases accelerated the pace of destruction.