Jökulsárlón is a lagoon full of icebergs, and the first view of it can leave you simply standing by the bike. The ice comes from Breiðamerkurjökull, a tongue of the great Vatnajökull ice cap, which has been retreating for decades and leaving behind a deep, cold lake. The lagoon appeared in the 1930s and has grown steadily as the glacier melts back, and it is now one of the deepest lakes in Iceland, with the bottom lying a couple of hundred metres below the surface. Blocks of ice in shades of blue, white and black, striped with volcanic ash, float slowly toward a short channel where the tide carries them out to sea.
Where the water meets the Atlantic, the ice is washed up on the black sand beach, and the glittering chunks scattered across it give it the name Diamond Beach. Seals follow the icebergs through the channel, feeding on the fish that come in with the tide, and you can often watch their heads popping up beside the bridge. Arctic terns nest nearby in summer and will dive at passers-by, and great skuas cruise the shoreline. The place is so photogenic that it has appeared in James Bond films, and boat tours with amphibious vehicles or inflatable boats run in summer.
The ride along the south coast is one of Iceland's finest. The Ring Road crosses the lagoon outlet on a bridge, and between the glacier tongues and the sea lies a flat black plain, a sandur, formed by glacial meltwater, where the road runs straight for kilometres with the ice cap hanging on the horizon. It is easy riding, with a good paved surface, but wind is the constant risk, because gusts can sweep across the plain without warning and carry sand and grit, and rain can arrive from the sea in minutes. Slow down on the one-lane bridges, and watch for sheep.
There is limited fuel in the immediate area, so plan your fills carefully. Höfn, about eighty kilometres to the east, is the main town with a full range of services, and the glacier area at Skaftafell to the west has more limited provisions. A small cafe by the lagoon sells soup and coffee, which is welcome in the cold air. Summer brings long days and the midnight sun, but crowds are heavy in the middle of the day, so early morning or evening visits are better, when the ice glows in a softer light.