A medieval monastic site and later Augustinian priory. The only standing remains are parts of a large, late medieval church and St Mochta's House, an undecorated, two storey, stone-roofed single cell building oriented to the east. Fragments of Romanesque sculpture are built into the wall and into the entrance gate post.

The site is thought to have been founded in the sixth century by St Mochta, but the monastery of the Virgin Mary (the present remains) was founded here in 1148. The early monastery was frequently plundered by Norsemen, among others. The names of a succession of abbots and bishops who were also associated with other monasteries at Slane (Meath), Duleek (Meath), Fore (Westmeath) and Clonkeen (Limerick), occur in the Annals. Louth was burnt in 1111, and again in 1133.

In 1135–38 Edan O'Kelly, Bishop of Oriel, fixed his See at Louth, and the monastic church became a cathedral. Augustinian rule was adopted at the site probably when St Malachy was legate (1140–48). The monastery was burnt in 1148 and refounded in the same year by Donough O'Carroll, king of Oriel. Louth was burnt in 1152, 1160 and laid to waste and burnt again in 1166. In 1242 the Archbishop of Armagh held a General Chapter there. In 1410 the valuation of the monastery was given as 400m, making it one of the wealthiest in the country. It was dissolved in November 1539.

The fragments could have come from the church destroyed in the fire of 1312, or may represent a destroyed architectural feature (chancel arch or doorway) from St Mochta's or part of a larger church of which St Mochta's formed the chancel.