Hekla remains one of Iceland's most formidable volcanoes, with some 20 unpredictable and devastating eruptions to its name. This might have something to do with its nickname: "Gateway to Hell" or, rather, "gateways", since numerous craters run along the length of a 40m fissure. It is not a difficult climb, and you will get to see extraordinary, chaotic landscapes made of lava flows, the age of which determines their colour.