Skip the hotel gym the next time you're in Continental Europe: head for a jog beside the Danube instead. This khaki-colored river (Johann Strauss must have been either color-blind or extending his poetic license when he put "Blue" into the title of his famous waltz) is lined with hiking and jogging trails that make it one of the region's best-kept recreational secrets.

The 2,850 km-long Danube kicks off in Germany's Black Forest and flows eastward through 10 countries to the Black Sea . Once part of the Roman Empire's border against barbarian hordes to the north — and of vital strategic importance to contending armies during the two World Wars — the Danube is now a more lighthearted place. On any given Sunday, whole stretches of it are abuzz with dog walkers and horse riders as well as runners.

Avoid the sections of the river that run parallel to the noisy, traffic-clogged autobahn, and stick instead to havens like the flat, unpaved trail that skirts the northern edge of Dillingen, a factory town of roughly 18,000 in Germany's

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nginx/1.14.0 (Ubuntu) southwest. Despite the proximity of urban development ( Munich is just a 45-minute drive away), the area is rich in wildlife. Look out for hungry ducks and other fowl dive-bombing a river teeming with fish, plus the occasional huntsman, struggling to get an overexcited dog to heel.

If you prefer hunting down cultural treasures, then call at one of the many historic towns and cities built on the Danube's banks. Budapest, Hungary's capital, is one of the most graceful. The Danube (or Duna in Hungarian) divides the city into the hilly side (Buda) and the flat side ( Pest ). Jog through the Buda side and you can check out the gorgeous 15th century Royal Palace and the 700-year-old Matthias Church. Pick up a trail on the Pest side for views of the neo-Gothic parliament building and the beautiful Central Market Hall. Can't choose between Buda and Pest ? No matter: there are three bridges connecting them so you can zigzag to your heart's content. Afterward, you can soothe your aching muscles with a soak at the city's famous bathhouses. Two top picks are the neo-Roman Gellert Baths and the Lukacs Baths, both on the Buda side of town.

If you enjoy distance running, the Danube's long, flat stretches offer rich opportunities. Among the best-known routes is that of the Linz Marathon, which kicks off every April in the Austrian town famous for its torte — an almond pastry with a lattice top over jam. Over 10,000 competitors took part in last month's race, and those planning to enter in 2006 should start training now. Those not contemplating anything quite as strenuous should get down to the riverside anyway. The fresh air and ever-changing riverscapes will have you waltzing through your workout.

• LARA WOZNIAK
• Looking for a 2,850-km jogging trail? Then try the banks of the Danube