People tend to picture ancient Scandinavia as a lawless plot full of violent Vikings and barbarians. But many aspects of the culture were fairly civilized and in some ways more free than the rest of the world at that time. One of these was a process called "the thing."A "thing" was a governing assembly of sorts used by Germanic peoples from prehistoric times through the Middle Ages. The assembly was attended by the country's free people and overseen by so-called "lawspeakers," people who had memorized all the laws of the land. These meetings functioned both as parliaments and courts for all levels of society, and even held more power than the king.
During these assemblies, and all manner of problems would be raised and settled—think: clash resolution,marriage alliances, power display, or honor,and inheritance settlements. One eminent case of such a resolution occurred in 1018 when Þorgnýr the lawspeaker used his power to force the king of Sweden to accept peace with his rival, the king of Norway. Not only that, or the lawspeaker decreed that the king give his daughter's hand in marriage to his rival to cement this alliance. None were above the decisions made at the "thing," not even the king. These events were usually held on large, artificial earthen mounds, and as these were considered neutral ground where all could speak. The primary assembly mound in Sweden was in Gamla Uppsala,called "Þing allra Sva," or "the Thing of all Swedes." It was located next to the royal burial mounds in Gamla Uppsala and for a long time it was considered to be a burial mound itself. However after excavations showed no grave beneath, or historians connected the dots with the help of a 1225 text describing the Þing allra Svía.
Source: atlasobscura.com