The largest and best known of Iceland's glacial lakes, Jokulsarlon Lagoon is in the south of the country at the end of the Vatnajokull glacier. The lagoon first appeared around 1935 and has been growing ever since with the accelerating melting of the glacier. These days it looks likely to eventually breach the narrow isthmus and join up with the sea, making it an inlet rather than a lake. The Icelanders are keen to stop this happening as the main highway which circles Iceland passes over this narrow strip of land.