Uppsalla was perhaps the most important site for the Norse pagans. They used to hold an assembly called the Thing of all Swedes and a sacrifice called Dísablót in honour of the disir (protective spirit).
The 12th century CE Danish chronicler Saxo Grammaticus thought that Odin himself had lived here, but the site was more widely associated with Ingvi Frey, who was known as the Lord of the Swedes. Christian accounts of Ingvi Frey sometimes call him the king of Turkey or a son of Odin, but he was in fact a far older deity and one of the most important. The Icelandic chief and author of the Eddas, Snorri Sturlusson, wrote that Ingvi-Frey had lived at Uppsalla. He was associated with sacral kingship and divine blood, and he founded the Yngling dynasty.
The 11th century CE German chronicler, Adam of Bremen, also wrote of the importance of Uppsalla to the pagans. He said that the temple there was covered in gold and that it contained statues of Odin, Thor, and Ingvi-Frey. Adam said that the people offered animal and human sacrifices to these idols and also to a nearby tree and a spring, both of which were sacred. They also worshipped heroic ancestors who had attained divinity in death by virtue of their great deeds in life. He said that a great ceremony was held there every nine years at the time of the spring equinox and that non-heathens also had to attend unless they paid a fee. Nine male animals of various species were sacrificed by hanging at this ceremony as well as nine men. The heathens were said to chant during these sacrifices.
The Ynglinga saga relates that a man named Frey had been buried in a barrow at Uppsalla and continued to bring good harvests even after his death, and people thought this would carry on for as long as Frey remained in Sweden. The Swedes then called him the god of this world and offered blood-sacrifices to him for peace and harvest.
Music used with permission: Faunus Amadeus Loki - Uuodan