Gamla Uppsala's mounds are securely dated to a real dynasty of kings, even where the temple a medieval chronicler described has never been confirmed by excavation.
Royal burials from a real period
Archaeological investigation has dated the site's three large burial mounds to the Migration Period, roughly the fifth and sixth centuries CE, and their scale and the high-status grave goods recovered from them are consistent with the burial of significant rulers, plausibly connected to the Yngling dynasty, a royal line later described extensively in Norse sagas as ruling this same region.
A church built where the old cult stood
A Christian church was constructed at Gamla Uppsala directly adjacent to, and by some accounts partly over, the site's earlier pagan cultic centre, a common pattern across converted Scandinavia in which a new church claimed physical and symbolic continuity with the older sacred site it replaced rather than being built at a neutral, unrelated location.
As this entry's companion article covers
Adam of Bremen's eleventh century written account describing a great pagan temple with elaborate sacrificial rites at Uppsala, and the gap between his description and what archaeology has actually confirmed on the ground, are addressed directly in this entry's companion article rather than repeated here.