Sentence:  “The swans are singing again,” said to one another the gods. And looking downwards, for my dreams had taken me to some fair and far <WSD>Valhalla</WSD>, I saw below me an iridescent bubble not greatly larger than a star shine beautifully but faintly, and up and up from it looking larger and larger came a flock of white, innumerable swans, singing and singing and singing, till it seemed as though even the gods were wild ships swimming in music. 
Meaning of the word marked with <WSD> tags:  An abode of the gods or afterlife in general.