Vikings first came to attack and plunder monasteries. They came from Norway and were known as "Norsemen". They sailed up the rivers in longships, attacking monasteries in search of treasures, leaving smoking ruins behind them. Monasteries in Ireland at that time were great centres of wealth. Many Viking raiders sailed home with their riches, while others began to settle in Ireland and to trade here. The first recorded Viking raid was the plundering in 842 by the 'heathens from Linn Duchaill'. Another followed in 845 by Vikings encamped on Lough Ree, who burned Clonmacnoise and its oratories.