Drive around Iceland's capital city of Reykjavik on any cold night and look at the houses and apartment buildings lining the streets. The first thing you may notice is how many windows are wide open, allowing the frigid outdoor air to mix with the warm indoor heat. In most places, the scene may seem a bit strange. But in a city that hosts the world's largest geothermal district heating system, it's a normal occurrence.

"We go beyond just energy. We use it to promote tourism, we use it for health and wellness, we use it for heavy industries and we also use it for educational purposes." -- Ólafur Ragnar Grímsson, President of Iceland