Arte TV had a special programme about the Nibelungen tonight.
It appears that many elements of the legend have historical grounds. The events took place in the 5th century, around 435 C.E. Some names were changed (e.g. Attila the Hun is called Etzel in the legend).
Although the fabulous treasure of the Nibelungs was never found in the Rhine, many specialists believe it existed and keep looking for it. One problem is that the Rhine of 1500 years ago was a series of very tortuous meanders, which have since become a straight line.
At the time, the Burgundians (=the Nibelungs) frequently crossed the Rhine to plunder Gallo-Roman towns and villages. They brought back with them gold, silver, jewelry and other valuables. Roman ship patrols on the Rhine forced them to cross in small groups at different places to increase their chances. In the process, they typically cut the looted objects into equal portions.
Some of these loots were found at the bottom of the Rhine, and notably also in a lake that once was on the trajectory of one of the river's meanders. The amazing find had hundreds of mutilated artifacts, now on display at the Historical Museum in Speyer.
This proves that the hundreds of pillaging raids could very well have led to the accumulation of a fantastic treasure. The Burgundians were eventually defeated by the combined Roman and Hunnic armies in the Ardennes Forest of Gallia Belgica. The royal family was entirely wiped out, leaving the place of the hidden treasure lost forever.
The Burgundians subsequently left the region of modern-day Worms and Speyer to settle in what was to become the Kingdom of Burgundy.
What is interesting is that soon after the desmise of the Burgundians, it was the Franks who would become the dominant power in the region, defeating the Alemani, the Visigoths, the Burgundians and conquering what was left of Roman Gaul.
How could this tribe that was frequently defeated by its neighbours suddenly reverse the course of history and give rise to the first truly European empire ? (see History of the Franks) Could it be that Siegfried of Xanten, had he been Frankish, told some Frankish friends about the place of Nieflheim, where the treasure was hidden ? After all, his hometown of Xanten was in Frankish territory.
Another clue is that Clovis I, shortly after his conquest of Gaul (486), married Clotide, the daughter of the King of Burgundy. A secret arrangement may have taken place between them, involving the recovery of the Nibelungs' treasure.