I love to see green repurposing of previously brown resources, things like tapping landfills for the methane gas they produce. A small town in the Netherlands is taking that principle and tapping abandoned flooded coal mines for its sweet green geothermal heat.
The town of Heerlen's Minewater system pumps hot water from the mines and pulls the heat out to power a closed loop system currently serving 350 homes and businesses. In the wintertime they pull the hot water from a depth of 2,300 feet for heat, in the summer they get water from a much shallower 820 feet deep and use it for cooling.
Check out this video of the Minewater project. it's in Dutch but has English subtitles. Awesome project.