It's always entertaining when really smart people get carried away. Olof Rudbeck was really smart. He could do pretty much everything. Unfortunately, "everything" included convincing himself that Hades, the Greek land of the dead, was located in Sweden.
Olof Rudbeck had a lot of brains, and he made good use of them. There were very few subjects he mulled over that he didn't feel the urge to dig into — sometimes literally. Once, as a medical student, he saw a dead calf. Wondering what the white goo inside it was, he dissected the thing and came up with a model for the lymphatic system. He was so distinguished a botanist that plants have been named in his honor. He built ships. He built houses. Oh, and he sang. Beautifully.
Sometimes, however, people misapply their accomplishments. Rudbeck, upon reading about ancient world, decided that it all must have started out in Sweden. After examining some burial mounds, he came to the conclusion that they were remnants from a civilization that started after Noah settled back on solid Earth — a civilization that spread across the world. Because Sweden was so old, and so advanced, he searched for evidence of it in old stories.
His first conclusion was that Sweden was Hyperborea. Hyperborea was an ancient Greek legend, a land "beyond the North wind," where the sun shone all day, and an idealized people dwelt in an advanced society. Rudbeck also decided that Jason and his Argonauts had visited Sweden, despite the fact that, if they had, their only way home would be through a network of Russian rivers and, at times, dragging their boat over land. Just to top it off, the Swedes were clearly the basis for Roman gods — the entire Roman pantheon, in fact. Hyperborean kings and queens would have been mythologized by the Greeks, their legends getting ever more grand, until they were eventually promoted to godhood by the Romans.
Not all of Rudbeck's conclusions were complimentary to Sweden, however. After reading about the many trips to Hades that various ancient Greeks had taken over the years, he began to believe that Sweden was the Greek version of hell. If they had come during the wrong time of year, Sweden would have seemed to them bitterly cold, damp, dark, and barren. They might have seen it as the underworld, from which they had to escape.
Eventually Rudbeck decided to promote Sweden to that gold standard of legendary homelands, Atlantis. He connected Swedish linguistics to various later cultures. He dated artifacts — partially inventing the practice of dating archaeological artifacts by the strata of the Earth that surrounded them. And he showed, at least to himself, that Sweden had the world's oldest and greatest culture.
He was completely wrong, but he was still very, very smart about it.