 The geographical notion of a continent stands in opposition to islands and archipelagos.Nevertheless, there are some islands that are considered part of Europe in a political sense.This most notably includes the British Isles (part of the European continental shelf and during the Ice Age of the continent itself); the islands of the North Sea, the Baltic Sea, and the Mediterranean that are part of the territory of a country situated on the European mainland; the Azores on the Mid-Atlantic Ridge, part of Portugal; and usually also the island states of Iceland (part of Norway and/or Denmark from 13th to early 20th centuries) and Malta.