The monument comprises the remains of St Columba's church. According to local tradition, the church of St Columba occupies the site of a cell of St Catan, who lived in the sixth to seventh century. On architectural grounds, however, the present church appears to be no earlier than fourteenth century. Margaret, daughter of Ruairi, chief of the Macleods of Lewis, was buried in the chancel in 1503. In 1506, the rector was John Macleod and in 1534 and 1536 Sir Magnus Vaus. Martin Martin, in 1695, records the church's dedication as being to St Collum (or Columba); as one of the two parishes of Lewis, Uidh had a minister, though by this time the principal church would probably have been in Stornoway.
St Columba's church is an elongated rectangle in plan, measuring some 20.5 by 7m overall and with its chancel facing north-east. It is built in rubble masonry, utilising the local gneiss, to which a red sandstone is added in later additions. A slight discernible difference in the construction of the eastern third, corresponding to the chancel area, probably represents different campaigns of work, rather than different periods; it may in any case be more apparent than real, being emphasised by the plaster which still adheres to much of the chancel walls. More certain is the evidence for the heightening or rebuilding of the upper part of the north wall, probably as part of a re-roofing operation. This may have occurred in the sixteenth century, and have been contemporary with the addition of a burial mausoleum to the west end of the church. The present door into the church is near the west end of the south wall. The original one may possibly have been in the west gable. The point of division between the nave and the chancel, still clearly visible, was evidently originally marked by a timber screen, with a loft above it, of which three supporting pockets for joists may be seen in the north and south walls respectively. There is also a small window for lighting the loft on the south, and what appears to have been a larger window (now blocked) below it, possibly for lighting an altar. Just inside the chancel, a narrow pointed-arched door in the south wall, opening outwards, probably led to a sacristy (now demolished). The altar, placed against the east wall, would have been lit by lancet windows in the south and east walls, though the pointed head of the latter was replaced by a lintel when the upper part of the east gable was rebuilt. The chancel was used in the fifteenth and early sixteenth centuries as a burial place for the Macleods of Lewis and their families.
Two grave-slabs which once lay here have now been set up against the walls. On the south is a slab showing a male figure wearing a long quilted coat, a camail of mail around his neck and shoulders, and a pointed helm. His left hand holds a sword. The man's identity is unknown, though it is possible that he was Roderick (Ruairi) Macleod of Lewis, who died around 1498. The second slab is fixed to the north wall, and shows an interlaced cross, with various animals in the foliage. An inscription around the margin (now barely legible) could at one time be read as follows: + HIC . IACET /. MARGARETA . FILIA . RODERICI . MEIC . LEOYD ./ [DE . LEODHUIS . VIDUA . LACHLA]NNI . MEIC . FINGEO[NE . OBIIT .] M V III.
The burial aisle added to the west end of the church has a low arch in its west wall, evidently intended to contain a principal tomb, and was lit by broad rounded-arched windows on three sides; access to it was by a rounded-arched door in the south wall, or by another slapped through the west wall of the nave. Rescue excavation in 1994 showed the burial aisle overlies earlier burials.
The area to be scheduled comprises a rectangular area of ground measuring some 37m SW-NE by 15m SE-NW, including the church, the burial aisle, the tombstones and an area of ground extending 4m from the church on all sides, as shown in red on the accompanying map.