SYAS RIVER

'Syas River' (, ) is a river in the Novgorod and Leningrad Oblasts of Russia. The Syas River flows from Valdai Hills north into Lake Ladoga. A town of Syasstroy is located at its mouth. The largest tributary is Tikhvinka River. Syas freezes up in November (sometimes in December or even January) and stays under the ice until April.
During the late Vendel Age and early Viking Age, the Syas River was popular as an alternative route to the Volkhov for penetrating from the Baltic Sea through portages to the Volga River. A fortress of Alaborg was built by the Vikings to guard the approaches to the Syas rapids. The route had declined by the 10th century.