The most famous aspect of Icelandic, and more broadly Norse, society is of course the Viking phenomenon. The Vikings (Old Norse víkingar) were the young warriors who sailed abroad each spring to raid the coasts and rivers of, predominantly, Europe. Their attacks were swift and brutal, and were made possible by the technology of their longships. These vessels were low and built around a flexible keel – thus the ship was shallow enough to navigate up rivers and malleable enough to brave the choppy waters of the North Atlantic. Before the longships, there were no warships in Europe that could access rivers, and so these waterways were not well-guarded, instead functioning as natural barriers. The Vikings took advantage of the low security, arriving at dawn to pull their ships up on the shores, rapidly raiding and pillaging before departing a few hours later, faster than the local lord could muster forces in response.