For more than half a millennium the Danube marked the frontier of the civilized world, the northern frontier of the Roman Empire. To the north lay mile after mile of muddy trails through dense forest, in the clearings of which resided the barbarians of Germania. It was dreary land according to Tacitus:

"Who would want to visit Germany with its unlovely scenery, its bitter climate, its general dreariness to sense and eye, unless it were his home?"

Tastes have changed markedly, it would appear, judging by the number of river vessels cruising the river today. Following the sack of Rome in 410AD, the German tribes spilled over the river into the vacuum of a declining civilization. It is from this time that historians date the beginning of the Dark Ages, so-called not just because the surviving evidence is scant, but because the light of Christianity was temporarily extinguished from continental Europe. In the last years of the Roman Empire, under Constantine, Christianity had become the most favored religion of a continent. Now the Barbarians were streaming through the gates.

Regensburg, a Roman frontier town of no mean repute, lived through these dramatic times to re-merge in the Middle Ages as the seat of the Imperial Diet, the parliament of the Holy Roman Empire and a pre-eminent cathedral city. The Holy Roman Empire was a loose confederation of mainly German states that sought a nostalgic, mystical, lyrical revival of the idea of a Christian Europe loyal to Rome. The first Holy Roman Emperor was Charlemagne - Karl der Grosser - crowned on Christmas Day of the Year 800AD. By this time Christianity, which had survived in the Celtic-speaking lands on the western fringes of Europe had been brought back to continental Europe by monks of largely Irish extraction. One of these heroes of the Early Christian Period, St Emmeran, re-established a Christian presence in Regensburg in 680AD.

On the site of St Emmeran's hermitage a monastic foundation grew up which had evolved by the Early Modern Period into a secular palace, home to the Thurn and Taxis family. Today Schloss St Emmeran is the largest privately owned palace in Germany. On our tour of the sumptuous interior of the palace we learned of how the family had first invented then monopolized the postal service for the Habsburg monarchy. This was the source of their subsequent wealth. The Habsburgs had in turn, by the fifteenth century, established themselves as sole candidates for the post of Holy Roman Emperor and by the eighteenth century the Imperial Diet had moved out of its mediaeval accommodation beside the cathedral and into Schloss St Emmeran. We were impressed both by the throne room and by a series of splendid public rooms in which the Imperial officials were lavishly entertained in the final century of the Holy Roman Empire's existence.

We then transferred to the heart of the old city to the visit the cathedral, noted for its tall towers and in stained glass. Regensburg is the home city of the present Pope, Benedict XVI, who used to enjoy playing the organ here. His brother was until recently the director of the Regensburger Domspatzen, the "singing sparrows" who can claim to be one of the oldest choirs in the world, in continuous existence for over a millennium. We ended the day exploring the maze of narrow streets in the mediaeval city, with their tempting shopping opportunities, and strolling beside the Danube admiring the historic stone bridge and savoring the wurst, sizzling on the grill of the world's oldest wurstkuchen.