Marcus Aurelius, emperor and philosopher, spent several years at Carnuntum during his wars against the Germanic tribes north of the Danube, and he is thought to have written part of his Meditations here; the third book carries the note that it was written at Carnuntum. In the second century, this was one of the most important places on the Roman frontier: a legionary fortress, an auxiliary fort and a civil town that grew into the capital of the province of Upper Pannonia, with tens of thousands of inhabitants. Today, the archaeological park at Petronell-Carnuntum and Bad Deutsch-Altenburg shows reconstructed houses, a bath and streets built using Roman methods, two amphitheatres, and the Heidentor, a great ruined triumphal arch standing alone in the fields. The Danube Limes became a World Heritage site in 2021.
The Danube flows past just to the north, and between Vienna and the Slovak border it runs through the Donau-Auen National Park, one of the last large stretches of floodplain forest in central Europe, with side channels, gravel banks, willows and poplars, home to beavers, kingfishers and white-tailed eagles. Bad Deutsch-Altenburg is a small spa town with sulphur springs, and the Hundsheimer Berge, low limestone hills to the south, offer dry grasslands and views over the river and the plains of Pannonia.
Riding here is pleasant rather than dramatic. The B9 runs from Vienna to Hainburg and the Slovak border with long straight stretches across farmland and vineyards, and the minor roads into the hills around Hundsheim and Prellenkirchen are narrower and more fun, with views towards the Leitha mountains and Lake Neusiedl to the south. Wind often blows across the flat land from the east, and in summer it can be very hot. Austrian motorways require a vignette, and speed limits on country roads are strictly enforced.
Petronell-Carnuntum and Bad Deutsch-Altenburg have cafés and small inns, and Hainburg, a medieval town with walls and gates on the Danube, has fuel and more choice. Try a glass of wine from the Carnuntum wine region, known for its red Zweigelt and Blaufränkisch, at a Heuriger, the local wine tavern, with a plate of cold meats, cheese and bread, and then head across the border to Bratislava, just a few kilometres away.