Armagh, with a population of 40,000, is the third largest city of Northern Ireland, after Belfast and Londonderry. Known as the "Cathedral City," it is the Irish seat of both the Roman Catholic and Church of Ireland (Anglican) churches. It is located about 40 miles southwest of Belfast. With origins dating back to the first millennium BC, the city of Armagh is one of Ireland's oldest settlements. The nearby Navan Fort, now one of the principal archeological sites in Ireland, was marked on a map of the known world by the Ptolemy in the 2nd Century AD. St. Patrick set up the first Christian church in Ireland here in 445 AD, and a church of some sort has occupied the hilltop site of the present-day Church of Ireland cathedral for more than 15 centuries. Armagh thus predates Canterbury as a Christian religious site. By the 8th Century AD, Armagh was one of Europe's best known centers of religion, learning and craftwork. The great Celtic chieftain Brian Boru, who died in battle against the Vikings near Dublin in 1014, is buried at the north side of the cathedral. Today's Armagh largely dates to the late 18th Century and owes its distinctive Georgian architecture to Richard Robinson, the Church of Ireland primate of that era. In 1995, Armagh was formally returned to city status.