PERNAU (in Russ. Pernov and in Esthonian Pernolin)  , a seaport and watering-place of western Russia, in the government of Livonia, 155 m: N. of Riga, on the left bank of the Pernau or Pernova, which about half a mile farther down enters the Bay of Pernau, the northern arm of the Gulf of Riga . Pop., 12,850 . The harbour is usually free from ice from the end of April to the middle of December . Founded on the right side of the river in 1255 by one of the bishops of Oesel, Pernau soon became a flourishing place . In the 16th century it was occupied in succession by the Swedes, the Poles and the Teutonic Knights . After 1599 the Poles transferred the town to the left side of the river; and in 1642 the Swedes, who had been in possession since 1617, strengthened it with regular fortifications . In 1710 it was taken by the Russians, and the fortress is now demolished .