You suddenly emerge into the Galilee chapel, built precipitously out over the banks of the river gorge - Norman architecture as light and delicate as the main church is weighty and dark. It is an exquisite contrast, and here, beneath the vigorously carved, almost Moorish, arches, you find the tomb of Bede, Saxon chronicler, poet, and saint. The Galilee chapel does everything that modern architecture is meant to do: a masterly handling of space, mass, and light. And it did it 800 years ago.

Galilee Chapel

Glorious though Durham is inside, it is its extraordinary setting that makes it one of the greatest buildings in the world. It is set at right angles to the peninsula, commanding all viewpoints. Its three square towers - one central, plus a pair at the western end - rise vertiginously high above the trees of the gorge, forming part of a complex of military and ecclesiastical buildings including the castle alongside, for so long home to Durham's mighty prince-bishops. The castle, cathedral and abbey buildings thus form a full-blooded, heroic composition.

The shrines to Cuthbert and Bede were destroyed in the Reformation, and in the 17th century the cathedral was occupied and vandalised by Scottish troops - who first used it as a barracks, and were later locked up inside as prisoners by Cromwell. But the church shrugged off such indignities, and even survived a Victorian restoration.

The Bishops of Durham made sure that the east coast railway line was pushed in a great curve on a high viaduct round the edge of the city, rather than smashed through the centre. As a result, railway travellers have one of the best views of this extraordinary building: "Half church of God, half castle 'gainst the Scot", as Sir Walter Scott observed. There is more to it than that. Durham speaks with ringing clarity from another, supposedly more primitive, age. It tells us that the highest art can emerge from conflict, conquest, and belief.