The site, known locally as Mount Offaly, is located along the Dublin-bound carriageway of the N11, some 700m southwest of Cabinteely Village. The topographic files of the National Museum of Ireland contain numerous references to the discovery of human remains from both the Mount Offaly site and adjacent properties. Two previous rescue excavations at locations to the north and northwest of the site recovered extended inhumations (1957, when the NMI excavated a long cist containing an adult male inhumation with some additional female bones, and 1991, when an unprotected inhumation was recovered from the root ball of a tree). A pre-development assessment undertaken in 1995 in advance of the construction of an Esso filling station revealed at least 14 in situ burials of early medieval date, as well as a sherd of Leinster cooking ware. Excavations undertaken between February and August 1998 revealed a complex sequence of burial, beginning at least around the 5th or 6th century and culminating sometime around the 11th or 12th century. At least 1,553 individual burials were uncovered, along with numerous deposits of disarticulated remains and two charnel pits. Six broad phases of burial are proposed for the cemetery.

Phase 1 burials were in earth cut graves, some of which were wood lined. Phases 2 and 3 burials occurred in earth-cut graves and stone-lined cists, accompanied by stone-lined sockets, possibly the location for a cemetery marker or grave alignment stone. The succeeding burial sequences of phases 4, 5 and 6 were exclusively in earth-cut graves, many of which were not clearly visible due to disturbance by successive interments. Numerous burials employed head stones (ear muff stones); in a few cases, pillow stones were used. The majority of the corpses were extended supine (flat on their backs), with the head to the west, although a number of variations were revealed.

The cemetery was enclosed by a series of three ditches, reflecting a sequential development or growth of the site. As the exact date of the phase 1 burials has yet to be established, it is unclear whether the cutting of the first enclosure ditch on the site took place prior to or later than phase 1. What is certain is that the inner ditch was filled in to facilitate the extension of the cemetery during phase 3, which entailed the excavation of a second ditch further east. The second ditch was filled in to facilitate the extension of the site at the close of phase 4, and a third and final ditch was excavated further east again to enclose phase 5. This latter ditch was filled in before phase 6 burial commenced. Other features uncovered included cobbled surfaces, charnel pits (including a stone-lined pit with a mill stone at the base), a bowl furnace and tentative evidence for a stone walled structure.

Burial postures suggest that the majority of the corpses were shrouded. At least three large shroud pins were recovered, athough only one was directly associated with a burial. Generally, the burials were laid in the extended supine position with the head to the west. However, a number were aligned with the head to the north or east, and this group also included several prone burials (face down) and at least one crouched burial (cut into the middle ditch fill). Two female burials contained full-term fetuses, one of which was in the breach birth position. Other unusual burials included an adult male from phase 3 with the body in an extended supine position but with the skull turned around to quite literally face west.

Post-excavation analysis

At the time of writing, the results of post-excavation skeletal analysis are not available. However, during the excavation, some obvious pathologies were noted, including a number of fractures, some showing signs of healing, dental and bone abscesses and compression fractures of the vertebrae. A number of other interesting features have also come to light during post-excavation analysis. There is at least one case of trepanation, and a number of weapon injuries are evident. In the case of one individual, the nature of the attack can be visualized. A diagonal 'sword' cut to the back extends from the upper vertebrae downwards and across the back of the left ribs. A fracture to the left arm was most probably incurred when the individual held it up to protect himself from a further blow, either from the left side or front, by a blunt weapon, possibly the broad side of a sword or bladed weapon.

A large assemblage of small finds was recovered from the site. This includes ferrous and non-ferrous metal, stone, bone, glass and ceramic. Some of the finds were directly associated with burials: three bone beads in separate infant burials; several pins, including one iron shroud pin; simple finger rings of bronze; and a number of iron knives. The majority of the finds, however, were recovered from contexts within the burial horizon. Some objects possibly represent material formerly associated with burials but that was disturbed by later re-cutting. Many artefacts of various types were recovered from contexts such as the enclosing inner and middle ditches. The finds assemblage includes shroud pins, stick and possible ring pins, iron knives, shears, gouges, D-shaped belt buckles, nails, bone and blue-glass beads, bone handles and double sided bone combs, one of which retained both decorated panels (dot and circle) held in place by four iron rivets. The pottery assemblage includes fragments of Phocaean red slipware, Bi amphora, D ware, E ware and several perforated 'lids' of unknown origin. Sherds of locally made Leinster cooking ware, datable to the late 11th or early 12th century, were recovered from later site contexts.

In summary, the excavations have revealed a portion of an enclosed cemetery that, by the nature of the burial phases and succession of ditches, clearly reflects a sequential development or growth of the site. The large number of finds of funerary, domestic and industrial nature suggests that the site was not used exclusively for burial and religious practices. Some objects are interpreted as the mounts and fittings for possible shrines or reliquaries, but there is also a large volume of butchered animal bone from the inner and middle ditches, a large (used) millstone derived from the base of the stone-lined charnel pit and features such as a furnace and hearths. Clearly, agricultural and industrial activities were undertaken on (or very close to) the site. During at least two stages, the area was possibly discontinued as a cemetery. At those times, cobbled surfaces were constructed (as well as tentative evidence for a structure) before the site reverted back to a burial ground. What is certain is that the range and types of objects recovered from the site, especially the imported pottery of 6th to 7th century date, suggest that the site is of considerable status and importance. The exact dimensions of the enclosure may only be estimated; however, it is reasonable to assume that within the boundary of the site lies evidence for perhaps a church, ancillary buildings, possible workshops and certainly further burials. Post-excavation is ongoing.