In the grey of early morn, Regensburg looks as though it might have been crafted by the maker of the first cuckoo clock. Sharp gabled roofs and pointed arches, spires soaring in heavenly aspiration, flying buttresses, vaulted ceilings, decorative portals and pinnacles - as Bavarian as bratwurst.
But as the first rays of sunshine filter through the laneways of the Old Town, a remarkable transformation takes place. The sun picks out the pastel colours of the houses, outdoor cafés spring into life and immediately the impression is Mediterranean. The arches and decorative arcades of the Romanesque era become more apparent, confirming the multiple personalities of Regensburg.
On the fringes of the Bavarian Forest at the confluence of the Danube and Regen rivers, Regensburg is often described as "Italy's northernmost city" for its flair and brio, and for the many reminders of its Roman heritage. Its large medieval centre is a UNESCO World Heritage site, an architectural distinction it has worn with pride since its listing in 2006.
Emperor Marcus Aurelius established a town here in AD179, and a portion of the northern Roman gate - the Porta Praetoria - is still visible today. The surrounding district, too, is littered with relics of nearly two thousand years of history. Regensburg has more than 1500 heritage-listed buildings, many of them dating back to the 9th century and nearly a thousand of them within the Old Town.
The Old Town is but one of Germany's 38 World Heritage sites - this number ranks equal fourth with France behind Italy (49 sites), China (45) and Spain (44) - and travellers can explore them in eight new routes focusing on the themes of historic town centres; architecture and design; nature, gardens and landscapes; industrial heritage; palaces and castles; cultural and spiritual heritage; and churches and abbeys.
Regensburg is the logical point from which to begin the route through Bavaria's treasury of medieval towns - a trail dubbed "Roman remains and Bavarian cheers" by the national tourist board - and as much as I hate the notion of the bucket list, it takes on a new meaning here. UNESCO's preservation program worldwide is something of a bucket-list in reverse. These are not just places to see before we kick the bucket, but places to see before they kick the bucket.
An impressive World Heritage visitor centre has been created in the old salt warehouses beside the Danube in Regensburg, bearing the UNESCO slogan "History full of life". Our guide, Matthias Freitag, makes this his mantra and he challenges us to identify examples on our Regensburg tour. We don't have to wait long.
One of Regensburg's most famous landmarks is the Old Stone Bridge over the Danube, proclaimed the "eighth wonder of the world" when it was completed in 1146. A canteen was built to feed the bridge workers and it's still here serving its original fare of Bavarian sausages, sauerkraut and sweet mustard. In no way is this the dying gasp of working-class catering. It remains popular among the bridge workers engaged in maintenance work following last year's record floods. The sausage kitchen, almost certainly the world's oldest fast-food outlet, sells about 6000 sausages a day. Make that 6002 - one bought tentatively and one enthusiastically.
In a city of such impressive architectural legacy, visiting the ancient sausage kitchen followed by the imposing Cathedral of St Peter might be going from the ridiculous to the sublime. The cathedral is regarded as the finest gothic building in Bavaria, although the work that was completed in the 19th century is unmistakably and confrontingly neo-gothic - construction took 600 years all up. On the wall facing the site of the former Jewish Ghetto is a stone carving depicting a sow suckling Jews, suggesting an ugly history of anti-Semitism. UNESCO and the Church must have agonised over compromising historical authenticity and removing it, or leaving it as a powerful reminder of an unpleasant past.
The residents of Regensburg might rather their city be remembered as the one-time home of Oskar Schindler, the German industrialist credited with saving the lives of 1200 Jewish people during the Holocaust, or the place visited by Pope Benedict XVI, who is seen around town when he returns to see his brother, Georg Ratzinger.
The ecclesiastical and the imperial were always cheek by jowl in Regensburg, and our guide soon has us panting up to the Altes Rathaus, the Old Town Hall, which dates from 1260 and remains a cornerstone of the city centre. Its vast Imperial Hall was the spot where Francis II abdicated in 1806 as emperor of the Holy Roman Empire. On the southern fringe of the Old City is the immense Thurn und Taxis family palace. Originally from Italy, the family created a mail route through central Europe in 1490 that became the German postal system. Princess Gloria von Thurn und Taxis still calls the palace home.
But it's not all history. There's life, too, as Freitag has promised. Our guide insists Regensburg is "not a fossil and not a museum" - about 15,000 of the city's 136,000 residents live within the 183-hectare Old Town. In medieval times Regensburg was a salt trading centre, which brought prosperity and a cosmopolitan atmosphere, both of which are still apparent today. Companies such as BMW, Siemens and Toshiba have plants here, and a university of 20,000 students injects youthful energy into the city. Regensburg, then, is both unimaginably old and robustly young.
The longest of our train journeys is a tick over two hours and takes us to Bayreuth, about 140 kilometres from Regensburg. Trains in Bavaria are punctual, clean and comfortable but prone to last-minute platform changes. And after a day immersed in the medieval, it comes as a surprise that the passengers are not clad in tunics and hooded capes.
Bayreuth's spectacular Margravial Opera House has UNESCO World Heritage status. Built between 1745 and 1750, it's regarded as the best-preserved example of Baroque theatre architecture. The lavish ceremonial style of the historic loge hall almost prompts visitors to genuflect, but the hall is in fact constructed from wood and canvas in the finest tradition of stage sets. The Opera House is undergoing extensive restoration and is scheduled to reopen in 2017.
Richard Wagner lived in Bayreuth from 1871 to 1876, and the town appears to remain totally in awe of the composer. Tourist brochures direct travellers to restaurants and hotels - including the stately old Goldener Anker - where Wagner often ate. Someone with whom I happen to agree once proclaimed, "Wagner's music is better than it sounds." There's no doubting his popularity here, however. His villa (now a Wagner museum), his grave, the church in which he and his wife, Cosima, were married, houses in which he lived (even the house in which his piano tuner lived), the Margravial Opera House and the Festspielhaus - the only opera house built specifically for the works of just one composer - are major attractions. If you're lucky enough to be guided by Heidi Zeitler, you'll get to hear delicious gossip about not only the musical achievements but the musical beds that spiced Bayreuth's cultural life.
For anyone who is not a Wagner groupie, however, Bayreuth's outstanding attraction is the Hermitage, or Old Palace, and Court Garden. The palace contains surprising Japanese and Chinese influences, and the gardens and parkland display traditional Baroque elements such as hedge gardens, pergolas and waterworks including upper and lower grottoes.
The Margravine Wilhelmine who stamped her style on the place was an imperious patron of the arts, and the famous composers, poets and artists who used to gravitate to Naples and Florence were soon seen swanning around her Bayreuth gardens. I walk in their footsteps, hands folded contemplatively behind my back, but their inspiration proves elusive.
Less than 90 minutes by train from Bayreuth is pretty Bamberg, inscribed on UNESCO's list of World Heritage sites as an outstanding example of a Central European city that has evolved around a medieval core. Bamberg has one of the largest intact old town centres in Europe, with more than 2400 listed buildings. During a long period of prosperity from the 11th to 18th centuries, its medieval and Baroque architecture influenced much of northern and eastern Europe. When Henry II became King of Germany in 1002, his vision was for it to become a second Rome. It's built on seven hills and the original medieval town followed a street plan in the form of a cross with a church at each of the four points.
Bamberg's great architectural moments are conveniently grouped in an old part of town known as the City on the Hills. This is the location of the late Romanesque and early Gothic Cathedral Church of St Peter and St George with its four majestic spires and its famous statue of the Bamberg Horseman; it is also home to the Baroque New Residence, the Old Court with its distinctive half-timbered buildings, and Michaelsberg Monastery. Swivel 360 degrees in the square in front of the cathedral to take in prime examples of the four main architectural styles of the city: Baroque, Gothic, Renaissance and Romanesque.
In delicious contrast to the sombreness of the ecclesiastic and imperial monuments, the eastern shore of Regnitz River has a brightly decorated row of half-timbered 19th-century (and earlier) fishermen's cottages affectionately dubbed Little Venice. This was always the bourgeois district of Bamberg and today is home to several university faculties and hip student cafés and bars.
For all Bamberg's architectural and religious significance, however, if UNESCO had not declared it a special place, Homer Simpson probably would have. This is beer heaven, a city of just 70,000 residents supporting nine major breweries and about 70 in the surrounding county, giving the region the highest density of breweries in the world. There are said to be 50 beer styles awaiting approval within the city's bars and brasseries.
It seems unlikely that Bamberg has ever been visited by a man with soul so dead he has not downed a half-litre mug of the city's legendary smoked beer. And who would want that claim to fame anyway? The brew derives its unique flavour from the practice of drying green malt over an open beechwood fire instead of the conventional hot-air method. An introduction awaits at the historic Schlenkerla brewery tavern, famed for its hospitality these past 609 years. So here goes: smells like a barbecue, tastes like maple-roasted smoked almonds - woody, smooth, sweet. It's a plausible explanation for the invention of beer-braised pork knuckles.
Würzburg, an hour and 20 euros by train from Bamberg, is dominated by Marienberg Fortress, which stands over the city like a protective parent. It's built on the site of a Celtic stronghold that dates back almost 3000 years. The first fortified castle was built here at the beginning of the 13th century and was the seat of the prince-bishops, the religious rulers of the region for the next 600 years.
Impressive as it is, though, it's not Würzburg's fortress that made it onto UNESCO's list of heritage treasures. The city's most prosperous period was during the rule of the art-loving prince-bishops of the Schönborn family in the 17th and 18th centuries. Between 1719 and 1744, the great Baroque architect Balthasar Neumann built for the Schönborns the "palace of palaces" - the Würzburg Residence, listed by UNESCO as one of Europe's most precious architectural treasures. Not that it's all about the architecture. To add a little interest to the ceilings, the Schönborns called in the Venetian artist Tiepolo to paint a vast fresco above the staircase and thus created one of the largest paintings in the world at about 600 square metres. The fresco and most of the palace escaped war damage, but much of Würzburg didn't.
On 16 March 1945, the RAF dropped 370,000 incendiary bombs, destroying 89 per cent of the city and killing more than 3000 residents. Moved by the lunacy of war, I spontaneously say, "Sorry about that," and my German guide politely responds, "That's okay." Seventy years after the event, neither of us mean what we say, but you can't let a statistic like that pass without acknowledgement.
Given the scale of destruction, it's remarkable that Würzburg remains one of Europe's most important examples of Baroque splendour. Romanesque style is brilliantly represented, too. The Cathedral of St Kilian, Germany's fourth largest Romanesque church, has recently been restored, tacitly confirming the belief that "if it ain't Baroque, don't fix it".
Kilian was an Irish monk who made a fatal error. He travelled to Würzburg to introduce Christianity to Franconia and succeeded in converting the reigning duke, who had married his brother's widow. She was not well pleased when Kilian advised the duke that this marriage was outside the laws of the Christian faith and she would have to go. While the duke was out of town on a crusade, she had Kilian and his two fellow Christian preachers beheaded.
While Upper Franconia, presided over by Bamberg, is all about beer, Lower Franconia and Würzburg are all about wine. Believing that if God disapproved of drinking, he would not have made wine so good, the prince-bishops of Würzburg created a vast imperial cellar beneath the Residence. Billed as one of the most beautiful in the world, the cellar holds about two million litres in oak plus 800,000 bottles. There are tours and tastings with commentary only in German, but the wine speaks all languages.
It's only appropriate, then, to sit out on the balcony of the Alte Mainmühle, a superb guest house and restaurant built in an old mill overlooking the Main River, and raise a glass of riesling and toast Bavaria and UNESCO. And as we do so in ancient Würzburg, modern Würzburg begins losing its head in a much nicer way than Kilian.
An impromptu jazz session begins on the old stone bridge across the Main, and the students answer the call and flock to the bridge from all directions. Preparations continue for the annual Africa Festival - the largest African music and culture festival in Europe - and the acclaimed Mozartfest and the International Film Festival and the Flamenco Festival and the JS Bach Festival and the Honky Tonk Festival.
Visiting these World Heritage cities is a chance to time-travel a thousand years and to realise that the greatest lesson of history is that we've learned so little from it. That, and to celebrate that fact that this medieval history is still so full of life.