The most quoted pages Adam ever wrote are a few chapters of his fourth book describing the sanctuary at Uppsala in Sweden, then still an active center of the old religion. He reports a temple ringed with a golden chain, holding images of three gods: Thor enthroned in the middle as lord of weather and crops, with Wodan the war god and Fricco the giver of peace and pleasure on either side. Every nine years, he says, a great festival drew all the Swedish peoples, and nine males of every living kind were sacrificed, their bodies hung in a grove beside the temple whose every tree was held divine.
No other medieval source describes Scandinavian public cult in anything like this detail, which is exactly why the account must be handled with care. Adam never saw Uppsala. He wrote from hearsay, in a missionary institution with every reason to dramatize the paganism it was sent to abolish, and some details echo literary models and biblical numbers. Archaeology at Gamla Uppsala has found a great hall and burial mounds but no unambiguous temple building matching his description, and historians continue to argue over how much of the picture is observation and how much construction. The atlas therefore records the Gesta as the indispensable and problematic source it is: the chief written witness to Norse religion, written by an outsider who never went north.