Lake Mývatn in the northeast of the country, is the fourth largest lake in Iceland. It's a strange meeting place of two worlds. The temperate and arctic zones, the flora and fauna of east and west. The lake and its associated river, the Laxá, is renowned throughout the ornithological world for its waterfowl. The area supports what is arguably the world's largest concentration of breeding ducks. It's the only place in Europe where Barrow's Goldeneye breed. A few pair of Great Northern Diver are present at the lake and Harlequin Duck are abundant around the Laxá river. All three are American species, Iceland is the only place in Europe where they breed.

Not only is the area interesting from an ornithological viewpoint, but also from a volcanological and geomorphological point of view. Nowhere else in the country is there to be found such a wide variety of natural wonders. The region is littered with a range of pseudo-craters, volcanoes of diverse sizes and hundreds of colorful sulphur pools. All the geological formations are recent, since Mývatn lies on the western edge of the volcanic belt that runs from north to south.

The lake is about 37 square kilometers in area, and very indented and irregular in shape. It's shallow, with an average depth of only about two metres and a maximum of just over four. Since the lake is so shallow, solar radiation is able to reach the bottom and there is teeming phytoplankton and other vegetation in the water itself. This is also partly due to spring water rich in nutrients, which drains into Mývatn from the east shore. There is therefore plenty of organic matter for animal life. This has been exploited by enormous swarms of midges and blackflies, which gather on the shores in calm weather, and are the most noticable of the lake's invertebrates. The name for midge in Icelandic is "mý", and this is where the lake's name is derived from. Mývatn means "Lake of the Midges".

The insect's larvae live on the bottom of the lake and form an important food source for the fish and ducks. The midges make their home in the lake and the blackfly larvae, which form the staple diet of Barrow's Goldeneye, Harlequin Duck and trout, are found only in the River Laxá. Billions of midge emerge from the lake at specific times during the summer. Although they don't bite, they form unbelievably enormous swarms, which can be very annoying. But the blackflies bite and can be unbearable. Their emergences are usually in June and August.

There are no fewer than 50 islands and islets at Mývatn, which offer a wide variety of nesting habitats. That and the rich food supply is largely to thank for the diverse and crowded waterfowl breeding. 15 species of duck nest in the area. Barrow's Goldeneye is abundant, with hundreds of pairs on the lake. The most common waterfowl are Scaup, Tufted Duck and Wigeon. Common Scoter is numerous, so are Red-breasted Mergenser, Long-tailed Duck, Mallard and Teal. Less common are Shoveler, Gadwall, Pintail and Goosander. Harlequin ducks are common on the River Laxá and Common Eider breed along the river'slower stretches. Pochard and Ruddy Duck have bred on rare occations and American Wigeon are seen every year. There is also a number of non-breeding Whooper Swans present in late summer. Other species to look out for include Horned Grebe and Red-necked Phalarope, which are both numerous. Almost all breeding species in Iceland are presented in the area, not including seabirds. A few pair of Gyrfalcon nest near the lake and can occasionally be seen gliding over.

The biggest attraction for European birdwatchers are, without a doubt, Barrow's Goldeneye and Harlequin Duck. The place to head for is a bridge over the Laxá river, in the south-west corner of Mývatn, where the main road to the north passes over. Fly-fishing is popular on the river and anglers frequent the area. The ducks are therefore used to humans and quite trusting. To see Harlequin it is best to walk upstream from the bridge. There will be plenty of birds coming downstream, or sitting on some of the many small islets that dot the river channel. Barrow's Goldeneye are to be found on the lake itself and the many surrounding ponds, while Harlequin Ducks are only on the river.