Helsinki, Finland is pioneering a huge cooling system that will use cold water from its lakes instead of of electricity-powered air conditioning, reports Fast Company.

"Hundreds of feet beneath an ordinary-looking downtown park, a local energy company built a huge reservoir filled with nearly 9 million gallons of lake water. When the system is fully operational next summer, the water will be pumped to local buildings in the area to keep them cool. At night, the water will flow back underground, where waste energy will be used to cool it down again."

(READ the full story from Fast CoExist)