The city of Armagh (from the Irish: Ard Mhacha meaning “Macha’s height”) is a large settlement in Northern Ireland, and the county town of County Armagh. It is an ancient religious site of worship of both Celtic paganism and Christianity. Armagh was granted a Royal Charter by Queen Elizabeth II in 1994, and city status was officially re-conferred in 1995. Armagh is the least-populated city in both Northern Ireland and the island of Ireland. It had a population of 14,590 people in the 2001 Census.
Foundation

Emain Macha (or Navan Fort) at the city’s edge, is believed to have been used as an ancient pagan ritual or ceremonial site. According to Irish mythology it was once the capital of Ulster, until it was abandoned during the 1st century. The site was named after the goddess Macha, and as the settlement grew on the hills nearby, it was also named after the goddess — Ard Macha means “The Height of Macha”.

When Christianity spread to Ireland during the mid-400s, Armagh became the island’s “ecclesiastical capital”, as Saint Patrick established his principal church there. Saint Patrick decreed that only those educated in Armagh could spread the gospel. According to the Annals of the Four Masters, in the year 457:
“     Ard Macha was founded by Saint Patrick, it having been granted to him by Daire, son of Finnchadh, son of Eoghan, son of Niallan. Twelve men were appointed by him for building the town. He ordered them, in the first place, to erect an archbishop’s city there, and a church for monks, for nuns, and for the other orders in general, for he perceived that it would be the head and chief of the churches of Ireland in general.     ”
source Wikipedia