Mahee is a large island, 3 km NE of Killinchy on the western shore of Strangford Lough.

As well as farms, and a ruined Norman Mahee Castle (see photo below) there is the ruins of an early Christian monastic site on the island It was built in 5th century by St. Mochaoi (St. Mahee).

References to the monastery begin in the 7th century and continue until a fire in 976, perhaps a Viking raid, when the abbot was burned in his house. In the late 12th century a small Benedictine monastic cell was founded on the site, but by 1306 the parish church was here, abandoned in favour of Tullynakill church on the mainland in the 15th century.
The glacial hill is crowned with three concentric walled enclosures. The middle cashel contained craft workshops and a schoolhouse. The inner cashel included the church with a graveyard and a later round tower to ward off Viking attacks. The sundial (on the right ) was reconstructed when the site was discovered in 1844. All these years the local farmers had grazed their sheep and cattle and not disturbed it.

There is an article in Lecale Miscellany 2002 about an iron axe head & bronze ringed pin.

Sketrick Castle

Sketrick Castle is situated on the western extremity of Sketrick Island which is in Strangford Lough and is now joined to the mainland by a causeway. It is off Ballydorn townland in Killinchy parish but was aligned to Ardkeen parish in the old days for taxation purposes.

There is a raised footpath from the mainland and the strait of water separating the two is nearly dry at low tide. Mentioned in written sources of 1470 as having been involved in warfare. A great army was lead by the O'Neill into Clannaboy to assist MacQuillan. They took Sketrick Castle and was given to MacQuillan for safe keeping.
It was actively involved in warfare in 16th century.It had 4 storeys with 4 chambers at ground level, the largest with a vault built on wicker centring and 2 brick-lines recesses, probably ovens. The central space may have been a boat bay and the small unlighted room could have been a lock-up or treasury.Bishops land taxed it at £1 in 1744

In 1833 is was described as a plain, stone building about 40 feet high, oblong in form and did not appear to have any flanking towers or outworks attached to it. The entrance faces west, being opposite the ford across the strait. The castle was not habitable then, being unroofed and open from the top to the ground. It stood complete until wrecked by a storm in 1896. The locals say that the Danes (Vikings) built it but it looks more like an Anglo- Norman construction.

The Montgomery Manuscripts states;" Other ancient family of the Savages is that of Archin (Ardquin ) Castle. It is of good account and hath another as they called Sketrick, the oldest of them all..." In the 1901 Census only one family called Montgomery lived here.

The island was bought by the Harrison family and was owned by Richard Harrison Esq. of Holywood House, as a portion of the Ardkeen Estate in 1870. (O'L V1 p 347) . Hugh Montgomery farmed on the island in 1910.