Nobody knew.

It ran for a hundred and fifty days' journey through deserts where nothing but flying serpents and satyrs lived, and the very lions' manes were burnt off by the heat....
'Good sporting there, at all events, among these dragons,' quoth Smid the son of Troll, armourer to the party.
'As good as Thor's when he caught Snake Midgard with the bullock's head,' said Wulf.
It turned to the east for a hundred days' journey more, all round Arabia and India, among forests full of elephants and dog-headed women.
'Better and better, Smid!' growled Wulf, approvingly.
'Fresh beef cheap there, Prince Wulf, eh ?' quoth Smid; 'I must look over the arrow-heads.' -- To the mountains of the Hyperboreans, where there was eternal night, and the air was full of feathers....

That is, one-third of it came from thence, and another third came from the Southern ocean, over the Moon mountains, where no one had ever been, and the remaining third from the country where the phoenix lived, and nobody knew where that was.

And then there were the cataracts, and the inundations-and-and-and above the cataracts, nothing but sand-hills and ruins, as full of devils as they could hold....

and as for Asgard, no one had ever heard of it....