Just off the highway linking Reykjavík to the International Airport at Keflavík, the glorious Blue Lagoon is Iceland's foremost spa. Its vividly coloured water, the outflow from a nearby geothermal power station, pools amongst a desolate mass of rough, black lava rubble. The lagoon's fine white silt is considered a cure for all manner of skin conditions.
There are grottoes, steam rooms and an on-site restaurant, so it's easy to spend a whole half a day soaking in this otherworldly location (and given the fairly steep entry fee, it's probably best to do just that).
Blue Lagoon Iceland
Not what you'd expect to find in the world's northernmost capital: a small white-sand beach, packed to capacity with locals on particularly sunny days.
Don't be fooled by their avid enthusiasm, though – the air temperature here rarely rises above 15ºC, though this is considered warm enough to strip off a shirt in Iceland. But two hot tubs steaming away at 38ºC, and a long, shallow pool full of geothermally heated seawater right on the sand, make Nauthólsvík pretty enjoyable whatever the season.
Located on the gravel plains at the edge of a shockingly stark wasteland of vivid orange rhyolite mountains, Landmannalaugar – the "Farmer's Hot Bathing Pool" – seeps out from under the edge of a 15th-century lava flow, where it mingles with a separate cold spring.
Edge into the cold water, walk upstream to where the two flows mix, find a spot where the temperature is perfect, and settle back to admire the dramatic scenery.
4. Laugardalslaug, Reykjavík
Icelandic pools have the convivial atmosphere of a bar or pub: many people enjoy a daily dip on their way to or from work, where they typically spend at least as much time gossiping with their friends as they do splashing about in the water.
This, the country's largest and best-equipped swimming complex, makes a great place to join in, with indoor and outdoor pools, hot tubs, saunas and water slides for children.
Iceland's early history is a mixture of Viking violence and cultured literary output. In no way is this better illustrated than through the life of Snorri Sturluson, a wily 13th-century politician believed to have authored the Eddas – works containing much of what is known about Nordic mythology – and several Icelandic sagas.
Snorri's scheming eventually led to his assassination; he was cut down in an underground tunnel here at Reykholt, northwest of Reykjavík, where you can still bathe in the hot pool he once used, temperatures allowing.
Another circular lava-block pool with Viking connections, this one was used by the outlaw Grettir to revive himself after he had swum the 4-mile-wide, ice-cold strait separating the mainland from the sheer cliffs of Drangey, his island of exile. The next morning found Grettir sheltering naked and painfully shrivelled in a nearby hall, where a bawdy servant girl taunted him mercilessly.
The pool is splendidly set on a remote stretch of Iceland's north coast, where you can ponder Grettir's achievements without, fortunately, having to replicate his swim.
7. Leirubakki, Hekla
Leirubakki is one of the few farms dotting the foothills of Hekla, a 1500m-high volcano whose regular eruptions have wreaked devastation since the Vikings settled in Iceland during the ninth century, and whose steaming slash of a crater was once believed to be the gateway to hell.
Leirubakki's circular, sunken pool is small – fitting about four people at once – and lined with cut lava blocks; views of Hekla rising up in the background more than compensate for the tepid water.
8. Jarðböðinn Nature Baths, Mývatn
If you're visiting Iceland in winter, hoping to see the northern lights, this Blue-Lagoon-esque spa in the hills above Mývatn – Midge Lake – is a great place to head. Miles from any large settlements and light pollution, there are views down over Mývatn's placid waters from the rim of the pool.
An added bonus are the tectonically unstable surrounds – boiling mud pits, volcanic cones, steaming lava from a 1988 eruption and even an underground bakery, heated by natural jets of steam.
9. Grjótagjá, Mývatn
Out in the countryside east of Lake Mývatn, Grjótagjá is a flooded subterranean volcanic fissure, which used to be a popular place for a swim until a nearby eruption in the 1970s heated the water up beyond tolerable levels.
But, lit only through the narrow entrance, claustrophobic and full of steam as it is, Grjótagjá is definitely worth a look – and, if you're around during the depths of winter, the water might just be cool enough for a brief soak.
Iceland's uninhabited interior is accessible for just a few short weeks during the summer, and if there's one place that demonstrates just how inhospitable the country can be it's Askja, a broad, flooded caldera surrounded by the jagged wreckage of countless eruptions.
Right on the lakeshore is Viti, a much smaller but even scarier crater created in a single colossal explosion in 1875 which blew debris as far away as Denmark. The pale blue water at the bottom is fine for a quick swim, but keep an eye on the smoking, sulphurous vents around the shore.
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