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:Château de Niort is a medieval castle in the French town of Niort. It consists of two square towers, linked by a 15th-century building and dominates the Sèvre Niortaise valley.
The two donjons are the only remaining part of the castle. The castle was started by Henry II Plantagenet in the 12th century and completed by Richard the Lionheart. It was defended by a rectangular curtain wall and was damaged during the Wars of Religion. In the 18th century, the castle served as a prison.
The present keeps were the central point of a massive fortress. The southern keep is 28m tall, reinforced with turrets. The northern tower is slightly shorter at 23m. Both are flanked with circular turrets at the corners as well as semicircular buttresses. Each of the towers has a spiral staircase serving the upper floors. The Romanesque architecture is of a high quality with the dressed stones closely jointed.