Jökulsárlón (literally "glacial river lagoon") is a large glacial lake in southeast Iceland, on the borders of Vatnajökull National Park. Situated at the head of Breiðamerkurjökull, it developed into a lake after the glacier started receding from the edge of the Atlantic Ocean. The lake has grown since then at varying rates because of melting of the Icelandic glaciers. The lake now stands 1.5 kilometres (0.93 mi) away from the ocean's edge and covers an area of about 18 km2 (6.9 sq mi). It recently became the deepest lake in Iceland at over 248 metres (814 ft) depth as glacial retreat extended its boundaries.The size of the lake has increased fourfold since the 1970s.It is considered as one of the natural wonders of Iceland.

source : http://en.wikipedia.org/wiki/J%C3%B6kuls%C3%A1rl%C3%B3n