The Perlan building in Reykjavik, Iceland. The structure was designed around 5 huge water tanks that hold geothermally heated water. This hot water is used to provide household heating as well as heating, schools, municipal buildings, and even used for keeping the capitals pavements ice and snow free in winter via a network or under pavement pipes. The geothermal water helps Icelanders to have a much reduced carbon footprint, as their heating is carbon free.