Conmacnois ("meadow of the sons of Nos") is one of the oldest monastic sites in Ireland. Founded by St. Cairan c. 545 CE it represents both the spread of Christianity through Ancient Ireland and the rise of the intellectual culture of early Christian Ireland. Clonmacnois was not only a monestary where people could devote themselves to prayer and meditation, but it was a thriving center of trade and education. It was, basically, an early university establishing a tradition of literacy at a time when Western civilization was under seige. The western Roman empire had collapsed in Europe, "barbarian" tribes were migrating southward altering the romanized culture of Gaul (France), Iberia (Spain) and even Italy. The collapse of the empire left a significant power vacume that could not be filled with a contemporary secular power, and though the Roman Catholic church attempted to fill the vacume, it too was essentially in retreat. In Ireland, however, the Celtic Catholic church flourished and pilgrimes and scholars came from the continent to the great monastic schools like Clonmacnois to pursue their spiritual as well as intellectual goals.

Strategically located on the Shannon River and the Esker Riada, Clonmacnois was a central crossroad between Linster and Connacht (east and west), and Ulster and Munster (north and south). St. Cairan chose the site for his monestary well. Though he would die only a year after the founding of his "city fair," the monestary would survive as a central religious and educational center until the Modern period (destroyed in 1547 by a combination of a fierce storm and looting by the British garrison at Athlone). The political importance of controling the monestary is demonstrated in the numerous royal tombs associated with the sacred enclosure including that of Rory O'Connor, last high-king of Ireland.

The ruins of Clonmacnois today boast significant archetectural features making a journey to the site a necessity for anyone interested in the history of Medieval Chrisianity or Ireland. The monastic enclousre (the sanctified territory marked by the boundary of the wall) includes seven temples (or chapel/oratories) as well as the central cathedral. Clonmacnois also contains three ancient high crosses dating from the 8th to 10th centuries. The temples are excellent examples of Irish/Romanesque Christian archetecture and are complemented by two round towers (unique features of Irish monastic communities).

Perhaps the most significant archetectural features associated with the monestary, however, are found outside the sacred enclouser (and are, therefore, often overlooked). The "Nun's Chapel" lies aproximately 200 yards east of the main enclosure. The remains of this chapel are excellent examples of Irish/Romanesque archetecture demonstrating the willing syncratism of Celtic Catholocism. In the arch and pillar detial one will find several examples of pre-christian iconography including the cult of the severed head (which can also be seen, in a varried form, in the arch of Clonfert Cathedral).