The Danish chronicler Saxo Grammaticus wrote that Odin himself chose to dwell at Gamla Uppsala, drawn by either the laziness of its inhabitants or the pleasantness of the spot. The Icelandic historian Snorri Sturluson told a slightly different tale, placing the god Freyr here instead, crediting him with building the great Temple at Uppsala and establishing the royal domains that would endure for centuries. Whether divine or merely legendary, by the 3rd century this site had become the religious and political center of the Swedes. The oldest Scandinavian sources speak not of a king of Sweden, but of the King at Uppsala, as if the place itself conferred authority. Every nine years, according to the medieval chronicler Adam of Bremen, a festival drew people from across Sweden. The sacrifices were brutal: nine males of every species, including humans, their bodies hung in a sacred grove where even the trees were holy.

The three great burial mounds called Kungshogarna stand as Sweden's oldest national symbols, dated to the 5th and 6th centuries. Folklore claims Thor, Odin, and Freyr rest within them, though 19th-century scholars speculated they held kings of the semi-legendary Yngling dynasty, rulers named Aun, Adils, and Egil. In the 1830s, when some academics dared suggest the mounds were natural formations rather than royal tombs, the future King Karl XV ordered excavations to settle the matter. The archaeologists found cremated remains and weapons, proof of elaborate Viking-age funeral rites. The dead kings had been burned at temperatures reaching 1500 degrees Celsius, their armor consumed alongside them so they might enter Valhalla properly equipped. The ashes were covered with cobblestones, then gravel and sand, then turf, building monuments meant to last millennia. Of the 2,000 to 3,000 mounds that once dotted this landscape, only 250 survive, the rest lost to farming and quarrying.

Gamla Uppsala clung to the old gods longer than anywhere else in Sweden. During the 1070s and 1080s, a renaissance of Norse religion flourished here, centered on the magnificent Temple at Uppsala with its wooden statues of Odin, Thor, and Freyr. When the Christian king Ingi refused to perform the traditional sacrifices, the people exiled him, electing Blot-Sweyn in his place. The name tells you everything: blot means sacrifice. But Ingi returned, killed Blot-Sweyn, and reclaimed his throne, beginning the end of public paganism in Sweden. Yet the site's sacred significance proved impossible to erase. In 1164, just decades after the temple fell, Gamla Uppsala became Sweden's first archbishopric. The Christians built their church atop or near the pagan holy ground, as they did throughout Europe. Today, beneath that church, archaeologists have found remains of large wooden buildings, perhaps the legendary temple itself, or perhaps an early Christian church deliberately built to claim this contested sacred space.

Anders Celsius, the astronomer who gave his name to the temperature scale, lies buried in Gamla Uppsala Church beside his grandfather Magnus. King Eric IX of Sweden was interred here before being moved to Uppsala Cathedral. Archbishop Valerius rests in this ground. The Thing of All Swedes met here from prehistoric times through the Middle Ages, a general assembly held each February or March in conjunction with the great fair called Disting and the religious celebration called Disablot. At these gatherings, the king proclaimed which ships would be levied for summer warfare. In 2000, the Swedish Asatru Society revived the tradition of holding blots at Gamla Uppsala, connecting modern pagans to a place where their spiritual ancestors worshipped over a thousand years ago. The mounds remain, silent witnesses to seventeen centuries of Swedish history, their grass-covered slopes concealing the ashes of kings who expected to wake in Valhalla.