Iceland is the world's 18th-largest island, and Europe's second-largest island after Great Britain. (The island of Ireland is third.) The main island covers , but the entire country is in size, of which 62.7% is tundra. Iceland contains about 30 minor islands, including the lightly populated Grímsey and the Vestmannaeyjar archipelago. Lakes and glaciers cover 14.3% of its surface; only 23% is vegetated. The largest lakes are Þórisvatn reservoir: and Þingvallavatn: ; other important lakes include Lagarfljót and Mývatn. Jökulsárlón is the deepest lake, at .