The Masurian Canal is a canal connecting the Lava River in Kaliningrad Oblast of Russia (a tributary of the Pregolya) and Lake Mamry, one of the Masurian Lakes in Poland. It was constructed between 1764 and 1776 under the auspices of Johann Friedrich Domhardt. It was modernised on several occasions, most importantly in the decade preceding the Second World War. The canal served as a defensive barrier between the Soviet and German armies. The damage it sustained during the war has never been repaired.