Archaeological work carried out by Dr Clare Ellis of Argyll Archaeology Ltd in advance of construction of an extension to the primary school on Iona has uncovered a ditch which could represent a previously-unknown section of the monastic vallum associated with Iona Abbey. The ditch is oriented roughly NNE/SSW and is around 0.60m deep and 2.80m wide. A stone revetment of around 0.5m in width runs along its south-eastern side; this stands on the base of the ditch, and can be seen on the stripped surface. The stone revetment appears to have been built to stop the adjacent sands from eroding into the ditch.
The remains of a turf bank with a cobble base were also identified. This bank is on the same alignment as the ditch, though it is notable that it has been cut by the ditch, indicating that it pre-dates this feature. However, the bank is on the same alignment as a modern wall, which was partially demolished in advance of the construction of the extension, and the existing school building, suggesting that that this land-division may have been maintained for over a thousand years. A fine gravel occurs below the ditch; this is at least 0.20m thick and contains numerous stone artefacts of prehistoric date. On the north-western side of the ditch is a buried brown silt loam, which also contained numerous lithics; this appears to be the remains of a buried prehistoric soil.
The monastic vallum, dating from the 7th /8th century AD, is present to the northeast of the primary school. This feature appears in parts to be constructed in a similar manner to the ditch observed at the primary school site, though the ditch at the primary school is much shallower. The turf wall is older than the ditch and both features appears to bound the original line of the road of the dead, as depicted on an estate map of 1769 and the OS 1st Edition map of the mid 19th century. It seems very likely that the turf bank and ditch are early medieval in date, perhaps 7th or 8th century, and may represent the remains of a hitherto unknown probable monastic boundary, while the underlying soils appear likely to date from the Iron Age or late Bronze Age.