Eyjafjallajokull, Iceland's sixth-largest glacier, gained worldwide recognition when the volcano lurking under it erupted in 2010. Large levels of volcanic ash caused air travel disruptions in Europe, and news reporters across the world struggled with the difficult pronunciation of Eyjafjallajokull, much to the amusement of us native speakers.
A less-known and less-tongue-twisting glacier is Ok, which is on a mountaintop in western Iceland. But Ok is no longer a glacier. The ice field that covered the mountain in 1900 - close to 15.5 sq km - has now been replaced by a crater lake.