Askja

The immense 50 sq km (19.3 sq mi) Askja caldera is remote, even for Iceland. Cold, windy and forbidding, it provides ample evidence of the creative power of nature. The original caldera was formed in 1875 when debris ejected from the volcano here made a mess as far away as mainland Europe.

A more recent depression has subsequently filled with water and, with a depth of 217m (712ft), is now the deepest lake in Iceland. The striking sapphire blue lake remains frozen most of the year, but a tiny, newer crater inside it is still hot and perfect for swimming.