This 12th or 13th century church ruin, the 9th century round tower and the remaining fragment of the 10th century high cross are located in the cemetery in the centre of Dromiskin village in Co. Louth, on the L7187, 11 kilometres (6.8 miles) south of the town of Dundalk and 3 kilometres (1.9 miles) north of the village of Castlebellingham. The name Dromiskin derives from Druim-ineas-clainn, meaning the "the ridge of the strong stream". Also to be found here are the ruins of a much later 19th century Church of Ireland parish church which was built in 1821.

The tower and high cross form the only remaining parts of the site of an ancient monastery that some state was founded by Lugaidh, son of Aenghus, King of Munster, a disciple of St. Patrick who had been baptized by him at Cashel, and who died in about 515 AD. Others posit that it was founded in the 7th century by St. Ronan, who died on the 18th of November 664 AD. In 801 AD the relics of St. Ronan, its second abbot, were placed within the monastery in a richly decorated shrine of gold and silver. This shrine is believed to have been eventually plundered by Viking raiders. A holy well in the village bears the saint's name.

The Annals of Ulster record that Dromiskin was burned by Vikings in 833 AD. It was subsequently pillaged by the Irish in 908 AD; by Domnall ua Néill, High King of Ireland from 956 AD to 980 AD, in 970 AD; by the Vikings in 978 AD; and by the Irish again in 1043 AD. Despite all of these attacks, the monastery continued in operation until the 12th century.

Very little remains of the original monastic site apart from the east gable end and some foundations stones of a small 12th or 13th century church. Only its later 15th century east-facing two-light window survives, with its dressed-stone jambs and single mullion with their holes for glazing bars, which are topped by elegantly carved ogee-framed arches. The filled-in sections of the earlier original taller window can still be seen in the east facade of the gable wall.

Near to the church's remains is the rather stunted-looking 9th century round tower. With a diameter of 5.25 metres (c.16.5 feet) and at just over 15 meters (c.50 feet) tall, it was entered through an east-southeast facing two-order Romanesque doorway, placed 3.7 meters (12 feet) above ground level. Decorated capitals still remain and outside of each are weather-word carved figures but its two supporting pillars are missing.

The upper portion of the tower was rebuilt around the 12th century and was used as a bell tower, functioning as such up until the 19th century. A cabin that had been built against the tower was removed in 1840 and a doorway that had, at that time, been broken into the tower at ground level was subsequently filled in.

As with most intact round towers, it is topped by a conical stone cap, but this dates from restoration work and a shortening of the tower by the Office of Public Works, which was undertaken in 1879. Also dating from the restoration period are the four rectangular windows below the cap which face to the cardinal points of the compass. The only window that is contemporary with the tower is the very high and small pointed-arch one that faces to the west.

Close to the tower, the head of a richly carved 10th century granite high cross was re-erected on a granite shaft in 1918. Weathering and erosion have long ago resulted in the carved scenes from the Bible being no longer clearly decipherable.

From Heritage Ireland