The Blue Lagoon is a magical place. The water is a pale, milky blue that just does not look real, with clouds of mist wafting upwards and fading into the mountainous backdrop. The water is warm, about 40 degrees, and the air temperature is between 5-15. So your head and shoulders are cold but your body hot; a strange but wonderful sensation.
The geothermal spa is in a lava field in Grindavík, close to the airport and about 40 minutes away from Reykjavik. It cost us 9700 ISK for transport to and from the Blue Lagoon, plus entrance fee. That's about $70. We thought that was pretty expensive, except that an Icelandic friend of mine confessed that she had been there 5 times, and I figured that if there was somewhere I was willing to spend $70 on in Sydney five times it was probably worth doing it once. Silly logic, I know, but I'm so glad we did go.
The lagoon has waters that are so rich in minerals like silica and sulphur that there is a research facility working on using it to find cures for skin diseases. The Blue Lagoon water forms when seawater mixes with volcanic magma from underground, merging to create a warm, sulphurous water. The fact this is all natural is amazing, and the water comes from a geothermal power plant nearby that exudes and endless cloud of steam into the copper skies; you can see it from the pool.
We had to have showers before and after swimming in the pool, in huge locker rooms and frosted shower cubicles, equipped with all the toiletries and equipment you need. They provide special mineral cleansing soaps and conditioner, as the water is not great for hair, although does wonders for the skin. The pool has several buckets of silica mud that you put on - a cool, white, gritty paste that I had lots of fun lathering on. My skin was baby soft afterwards.
The Blue Lagoon website has all the pricing, accomodation and food details :)