The abbey began with a false start. Monks came out from Corbie, in Picardy, in 816 and set up a dependent house, but the site turned out to be badly chosen, and in 822 they moved to a spot near a place then called Villa Huxori. They named the new house Nova Corbeia - the new Corbie - which wore down over the centuries into Corvey.

Its first abbot, Adalard of Corbie, was a cousin of Charlemagne, and the connections showed. Ansgar, later remembered as the Apostle of Scandinavia, founded the abbey school in 823. Corvey became independent in 826 under the patronage of Saint Stephen, and in 833 it was granted the right to strike coin, the first place east of the Rhine to hold it. Books came from Corbie and then from Corvey's own scriptorium, and the school produced scholars for generations, among them the tenth-century historian Widukind of Corvey.

The western block that faces you today was built between 873 and 885, and it is the oldest surviving westwork anywhere - a monumental entrance structure with a vaulted hall on the upper floor and galleries running round the main space. Almost every great Romanesque and Gothic church front in western Europe descends from the idea worked out here. It is also the oldest medieval building still standing in Westphalia.

Inside, on the walls of the upper hall, is something with no parallel at all: Carolingian wall painting of scenes from classical mythology, Odysseus among them, read for Christian meaning. Ninth-century monks looking at Odysseus and his crew and finding a sermon in it is not what most people expect of the period, and no other Carolingian building has kept anything like it. UNESCO inscribed the westwork in 2014, together with the buried remains of the settlement that grew around the abbey, as the Carolingian Westwork and Civitas Corvey.

Corvey sat where the great east-west road called the Hellweg met the river, and that position made it rich and useful. The abbey's historian H. H. Kaminsky counted at least 110 visits by the royal entourage before 1073 - occasions on which charters were issued and business was done.

A diploma from Otto I in 940, the first of its kind, shows what that meant on the ground. The abbot Folcmar was granted powers of enforcement over the peasants of the abbey's lands, who were to take refuge in the fortress on monastic ground and, in exchange, were expected to keep it in repair under his supervision. The workforce was drawn from three districts under four counts, and the counts were explicitly barred from demanding the same labour. The arrangement protected these people. It also assigned them, and the document is careful about which lord's claim came first.

Corvey took sides. In the Investiture Controversy its abbot stood with the Saxon nobles against Emperor Henry IV, and the abbots Markward and Erkenbert carried the house through the crisis - Kaminsky rates Markward, who served from 1081 to 1107, among the most important in the abbey's thousand-year history. It was a centre of eleventh-century church reform and founded daughter houses across the region.

The end came in 1634. Imperial troops sacked the abbey during the Thirty Years' War and laid siege to Höxter alongside it, and the buildings were subsequently demolished. The westwork alone was left standing, which is why the oldest part of Corvey is now the only old part. A Baroque palace and church went up around it later in the century. The abbey was elevated to a prince-bishopric in 1792, then secularised in 1803 in the general redistribution of German church lands and absorbed into the short-lived Principality of Nassau-Orange-Fulda.

The princely library that filled the rebuilt palace ran to roughly 74,000 volumes in German, French and English, with buying largely tailing off around 1834. Its English holdings turned out to matter: Corvey collected popular novels of the Romantic period so completely, and so indiscriminately, that it preserved editions found in almost no other collection, and scholars now go there to read fiction that England itself threw away.

Its most famous librarian arrived in 1860. August Heinrich Hoffmann von Fallersleben had written the Deutschlandlied nearly twenty years earlier, in 1841, and spent his last fourteen years here among the books. He died in 1874 and is buried in the churchyard. Corvey remains in private hands - the present owner is Viktor, 5th Duke of Ratibor and 5th Prince of Corvey, born in 1964 - and the palace, the library and the church are open to visitors.