It is a by product of the nearby Svartsengi geothermal power plant. The warm waters are rich in minerals like silica and sulfur and bathing in the Blue Lagoon is reputed to help many people suffering from skin diseases such as psoriasis. The water temperature in the bathing and swimming area of the lagoon averages 40 °C (104 °F) and is enjoyable year round, even in freezing conditions.
Adhere to the signs:
It takes approximately 20 minutes to drive from Keflavik International Airport to the Blue Lagoon and 45 minutes to drive from downtown Reykjavík to the Blue Lagoon. There is lots of free car parking.
There are lots of tour companies offering all inclusive package deals.
Reykjavik Excursions  and Iceland Excursions  run all inclusive trips from Reykjavík. There are tickets available that make it possible to call in en-route between Keflavík Airport and Reykjavík, or vice versa.
Many taxi companies offer trips to the Blue Lagoon, with the taxi waiting while the visitor enjoys the Blue Lagoon and its surroundings. Note that this option can be extremely expensive.
Blue Lagoon has its own Skin Care Products, which are very expensive.
There is also a gift shop (also down town and at the international airport in the duty-free section).
There is a cafeteria and a restaurant. The cafeteria has a decent selection including Soups, Hot Dogs and other snacks, prices are a little inflated but reasonable. The restaurant is a little expensive.
There are water fountains in various locations to keep you from dehydrating. The Cafeteria has a selection of drinks
The Blue Lagoon Clinic has accommodation for both treatment and non-treatment guests.
The Northern Lights Inn is nearest hotel, about 1km from Lagoon. It offers guests free transfers to and from the Blue Lagoon and Keflavík Airport and has a good restaurant.
Accommodation can also be found in the nearby town of Grindavík.