"It's said to be one of the most unearthly places on earth and quite spectacular.
Hverarönd is an area near Mývatn in the northeastern part of Iceland. The area has a lot of geothermal energy which shows itself in the form of bubbling pools of grey mud and sulphur. As a result of this the area smells rather strongly of sulphur but experiencing the almost alien-like landscape is well worth the smell." http://www.planiceland.com/vtours/myvatn_hverir/