The building in the background is an ancient Christian church. The earthen mounds are Viking era burial sites. Many people think the Temple of Uppsala stood were this church now stands. The Christians had a habit of razing Heathen temples and building churches over the site as a sign of victory.
Medieval drawing from Adam of Bremens description of the Heathen temple
Temple of Uppsala and Dísablót
The Temple of Uppsala
Around the year 1070, Adam of Bremen described the great pagan cult centre of Uppsala, Sweden in his work Gesta Hammaburgensis ecclesiae pontificum, the most famous source to pagan ritual practice in Sweden. It was written with the agenda of showing how barbaric and immoral were the practices and religion of the pagans, in defense of the still somewhat fragile position of the Christian church in Sweden at the time. Thus it cannot be read as an objective source to paganism, but rather as a strongly biased attack on paganism. Yet it is one of the only sources we have, and must make do with. The temple of Uppsala is described in the fourth book, chapter 26:
“This people have a widely renowned sanctuary called Uppsala. By this temple is a very large tree with extending branches. It is always green, both in winter and in summer. No one knows what kind of tree this is. There is also a spring there, where the heathens usually perform their sacrificial rites. They throw a live human being into the spring. If he does not resurface, the wishes of the people will come true.
The Temple is girdled by a chain of gold that hangs above the roof of the building and shines from afar, so that people may see it from a distance when they approach there. The sanctuary itself is situated on a plain, surrounded by mountains, so that the form a theatre.
It is not far from the town of Sigtuna. This sanctuary is completely covered with golden ornaments. There, people worship the carved idols of three gods: Thor, the most powerful of them, has his throne in the middle of the hall, on either side of him, Odin and Freyr have their seats. They have these functions: “Thor,” they say, “rules the air, he rules thunder and lightning, wind and rain, good weather and harvests. The other, Odin, he who rages, he rules the war and give courage to people in their battle against enemies. The third is Freyr, he offers to mortals lust and peace and happiness.” And his image they make with a very large phallus. Odin they present armed, the way we usually present Mars, while Thor with the scepter seems to resemble Jupiter. As gods they also worship some that have earlier been human. They give them immortality for the sake of their great deeds, as we may read in Vita sancti Ansgarii that they did with King Eirik.”
Fourth Book, chapter 27:
“The sacrifice happens as follows: Nine live beings of the male gender are sacrificed, their blood is used to mollify the gods.
For nine days they celebrate with banquets and such sacrifices. Every day they sacrifice one man – together with other living beings, so that within nine days 72 living beings are sacrificed. This sacrifice takes place in connection to the spring equinox.
The bodies are hanged up in a grove close to the temple. This grove is so holy for these heathens that they think that each individual tree inside it has become divine through the death and decay of the victims. There hang dogs and horses together with humans. A Christian told me that he had seen 72 such bodies hang there, animals and people together. As usual with such sacrificial acts, many songs are sung, they are indecent and ought to be concealed.”
Read the rest of this very interesting article here.