According to the Hypatian Codex that was created at the end of the 13th century, the legendary Varangian leader Rurik arrived at Ladoga in 862 and made it his capital. Rurik later moved to Novgorod and his successors then to Kiev where foundations for the powerful state of Kievan Rus' were laid. There are several huge kurgans, or royal funerary barrows, at the outskirts of Ladoga. One of them is said to be Rurik's grave, and another one—that of his successor Oleg. The Heimskringla and other Norse sources mention that in the late 990s Eric Haakonsson of Norway raided the coast and set the town ablaze. Ladoga was the most important trading center in Eastern Europe from about 800 to 900 CE, and it is estimated that between 90% to 95% of all Arab dirhams found in Sweden passed through Ladoga.