The city's Anglican cathedral occupies the site of St Patrick's original stone church. The present cathedral's ground plan is 13th century, but the building itself is a Gothic restoration dating from 1834 to 1840. A stone slab on the exterior wall of the north transept marks the burial place of Brian Ború, the high king of Ireland, who died near Dublin during the last great battle against the Vikings in 1014.
Within the church are the remains of an 11th-century Celtic Cross that once stood nearby, and the Tandragee Idol, a curious granite figure dating from the Iron Age. In the south aisle is a memorial to Archbishop Richard Robinson (1709–94), who founded Armagh's observatory and public library.