Inside the enclosure Felső had erected reed platforms and shelves raised well above ground. "Those are to protect articles during floods," Felső said. "The water often gets this high," he added, holding his hand just below his heart. He already stood about eight feet (2.4 meters) above the river's surface.

As I ate crispy chunks of fish, Felső produced an aerial photo of his park showing irregularly shaped ponds connected by winding man-made channels. Centuries ago this system irrigated pastures and orchards growing dozens of varieties of apples, pears, plums, and cherries. Fish were raised in the ponds and trapped by wicker fencing when floodwaters receded.

The system declined in the 16th century, disrupted when a huge Turkish army crossed central Europe to secure the western reaches of their empire. By the end of the 19th century the serpentine Danube had been forced between dikes put up to create land for growing grains.

Back in the boat after lunch, Felső pointed out rock piles that the park is spacing out on either side of the river in a staggered pattern designed to force the water to assume a more natural winding course, a result that will take up to two decades to achieve.

The river that day was broad and serene, colored dark green in the shade of half-drowned trees. "This environment is good for birds that need lots of water," Felső said. Indeed, the 122,000-acre (49,400-hectare) park harbors an abundance of bird species. "We''ve got eagles, falcons, herons, and 40 pairs of black storks. This park may be their last chance."

South of Duna-Dráva scars of war began to appear, reminders of the conflict ten years earlier between Croatia and Serb-dominated Yugoslavia, which here face one another across the Danube. In Bilje bullet holes pockmark the headquarters of Kopački Rit Nature Park. From there biologist Tibor Mikuska drove me to a levee whose thick grass conceals countless mines left from the war.

Mikuska pointed to a path worn through the grass that led down along a safe section of levee to a concrete bulkhead. Such trails are left by anglers, and many of them were out that fine day, casting lines into waters teeming with fry. Commercial fishing was outlawed here in the 1970s, and Mikuska wants to restrict sport fishing to the park''s least environmentally sensitive areas.

"The park should be open to the public, but people can no longer just go in and do what they want," Mikuska said. Shooting waterfowl is now outlawed, and park staff hope to limit big-game hunting. They are also training locals as nature-tour guides and encouraging them to open their homes as bed-and-breakfasts. "We want to make people proud of this area."

Kopački Rit and other Danube preserves work under the rubric "sustainable": Steer locals away from practices that harm the ecosystem and encourage approaches that are less injurious but that still provide a decent living.

The contrast between Blue Danube nostalgia and reality couldn't be sharper than in Yugoslavia, which was bombed by NATO to halt President Slobodan Milosevic's attacks on ethnic Albanians in the southern province of Kosovo.

Sitting on the Danube 47 miles (76 kilometers) upstream from Belgrade, Novi Sad suffered mightily, with an oil refinery and three bridges destroyed. There, in a neighborhood of modest houses, a tearful woman named Jasminka Bajic smoked and drank tiny cups of strong Turkish coffee, recounting how she lost her husband, Milan.

"It was 12:20 a.m. on June 8, 1999," she recalled. "No one expected the bombs to hit that close to the houses." Milan was in the doorway of their home when a bomb landed across the road. "I had to sell all my cattle to buy the gravestone," she said. Jasminka now works as a janitor for a local labor union. As compensation for her husband''s death, his employer built a new house for her and her two daughters.

Later that day at a small marina I met a fisherman named Velimir Teodorovic, who also has vivid memories of the NATO bombing. In his boat we sped toward two enormous concrete slabs sticking out of the water.

The slabs, remnants of the Freedom Bridge, formed a V with its point below the surface. Teodorovic nosed the boat onto one of the slabs, walked up its surface, and pointed downriver.

"I was right there, fishing for sturgeon and catfish, when the first rocket hit," he said. "People got out of their cars and started running back up the bridge, but I yelled at them to get into my boat because more rockets might hit." Sure enough, two more struck just after seven people scrambled aboard.

When we returned to the marina, I was struck by another Danube contrast: people in white lawn chairs under shade trees, drinking and laughing within the sobering sight of the bombed bridge.

The NATO attacks caused billions of dollars of damage and took a reported 500 lives. At risk were hordes of Serbian refugees who had fled from Kosovo to northern Serbia, where thousands remain. In Belgrade I went to a recreation center crammed with 33 refugee families. Small patches of territory, most of them no more than ten feet square (one meter square), were partitioned with blankets and plastic sheets.