Sineus and Truvor were the brothers of Rurik, a chieftain of the Varangian Rus tribe considered to be the founder of the Rurik dynasty, which ruled the Kievan Rus. According to the Russian Primary Chronicle, the town of Izborsk was the seat of Truvor from 862 to 864. Although his burial mound is still shown to occasional tourists, archaeological excavations of long barrows abounding in the vicinity did not reveal the presence of the Varangian settlement at the site, which indicates that Izborsk was an important centre of the early Krivichs.
Truvor's gorodishche is a settlement about half a kilometer north from the fortress that came about in the late 7th and early 8th century, and proceeded to grow twice in size in the 10th and 11th centuries. It was the predecessor of the Izborsk Fortress, protected by an oakwood wall which was later upgraded to stone, 3 meters in height by 3 meters in width in the 12th century. Though Truvor's gorodishche is mostly destroyed, a small part of the wall remains today.
References:Visby Cathedral (also known as St. Mary’s Church) is the only survived medieval church in Visby. It was originally built for German merchants and inaugurated in 1225. Around the year 1350 the church was enlarged and converted into a basilica. The two-storey magazine was also added then above the nave as a warehouse for merchants.
Following the Reformation, the church was transformed into a parish church for the town of Visby. All other churches were abandoned. Shortly after the Reformation, in 1572, Gotland was made into its own Diocese, and the church designated its cathedral.
There is not much left of the original interior. The font is made of local red marble in the 13th century. The pulpit was made in Lübeck in 1684. There are 400 graves under the church floor.