Hereford Cathedral is the cathedral church of the Anglican Diocese of Hereford in Hereford, England. A place of worship has existed on the site of the present building since the 8th century or earlier. The present building was begun in 1079. Substantial parts of the building date from both the Norman and the Gothic periods. The cathedral is a Grade I listed building. The cathedral has the largest library of chained book in the world, its most famous treasure being the Mappa Mundi, a medieval map of the world created around 1300 by Richard of Holdingham. The map is listed on the UNESCO Memory of the World Register. Origins The cathedral is dedicated to two saints, St Mary the Virgin and St Ethelbert the King. The latter was beheaded by Offa, King of Mercia, in the year 794. Offa had consented to give his daughter to Ethelbert in marriage: why he changed his mind and deprived him of his head historians do not know, although tradition is at no loss to supply him with an adequate motive. The execution, or murder, is said to have taken place at Sutton, four miles (6 km) from Hereford, with Ethelbert's body brought to the site of the modern cathedral by "a pious monk". He was buried at the site of the cathedral. At Ethelbert's tomb miracles were said to have occurred, and in the next century (about 830) Milfrid, a Mercian nobleman, was so moved by the tales of these marvels as to rebuild in stone the little church that stood there and to dedicate it to the sainted king. Before this, Hereford had become the seat of a bishopric. It is said to have been the centre of a diocese as early as the 670s when Theodore of Tarsus, Archbishop of Canterbury, divided the Mercian diocese of Lichfield, founding Hereford for the Magonsæte and Worcester for the Hwicce. In the 7th century the cathedral was refounded by Putta, who settled there when driven from Rochester by Æthelred of Mercia. The cathedral of stone, which Milfrid raised, stood for some 200 years, and then, in the reign of Edward the Confessor, it was altered. The new church had only a short life, for it was plundered and burnt in 1056 by a combined force of Welsh and Irish under Gruffydd ap Llywelyn, the Welsh prince; it was not, however, destroyed until its custodians