My favorite part of Iceland was going to the Blue Lagoon. It is close to the airport and it is really cool. The water was really warm and really blue.
Here is a link to a live webcam of the Blue lagoon! http://www.bluelagoon.com/Geothermal-spa/live-webcam/
From the Blue Lagoon website it says "The lagoon holds six million liters of geothermal seawater, which is renewed every 40 hours. Regular sampling shows that “common” bacteria do not thrive in this ecosystem, thus additional cleansers such as chlorine are not needed. The Blue Lagoon geothermal seawater is a part of an ecocycle where nature and science work in harmony. The seawater originates 2000 meter/6562 ft beneath the ground where it is heated by earth’s natural forces. At this depth the temperature is 240°C/464°F and the pressure is 36 times the pressure on the earth’s surface. The geothermal seawater comes into contact with cooling magmatic intrusions and captures the earth’s minerals, resulting in this unique natural source known for its healing power and actives. "